In a Mirror, Darkly (episode)
In the mirror universe, Commander Archer mutinies against Captain Forrest in order to capture a future Earth ship found in Tholian space. (Part 1 of 2)

Summary

Teaser 
April 5, 2063 – From beyond Earth's atmosphere,  descends and lands in Bozeman, Montana. Watched by a crowd of onlookers, a member of the Vulcan crew disembarks and approaches . The alien performs a Vulcan salute and recites a Vulcan salutation: "Live long and prosper." Cochrane tries to imitate the newcomer's salute. After an unsuccessful attempt, he lowers his hand and, instead of holding it for a handshake (which is what happened in a similar parallel universe), he reaches into his coat and pulls out a shotgun with which he shoots the Vulcan, who instantly collapses. A bearded man in the crowd tells the other Human spectators to board the alien ship and take everything they can. Then the crowd storms the Vulcan craft with guns and attack the crew.

Act One 
"Captain's starlog – January 13, 2155. We've left Gorlan Station and have set a course to rendezvous with our assault fleet. Major  and the doctor have asked for a few minutes to show me their latest project."

Aboard the , Reed and Dr.  demonstrate their new invention of an agony booth to Captain Maximilian Forrest and First Officer , using the booth on a Tellarite officer named Terev. The observers discuss attributes of certain torture methods. Although Reed is unsure why Terev is being punished, the Major believes all Tellarites are guilty of something. Captain Forrest exits, followed out by Archer.

In a corridor, Archer reminds the captain of a proposal he made to venture into Tholian space, as Archer has received news of a technology there that would give the Terran Empire the upper hand against a rebellion. However, Forrest wants to help the Empire's assault fleet annihilate the rebels, as ordered by . Although Forrest suspects that Archer wants to use the technology to attain personal glory, the first officer repudiates this. Archer's insistence on his plan influences Forrest to threaten the first officer with a place in the agony booth. Archer finally yields to Forrest's authority.

Forrest is later busily reviewing work in his quarters when , the captain's woman, approaches, eager to relax him. They kiss passionately, Forrest conceding to her advances. Hoshi remarks that she is likely the only person aboard who doesn't want to kill him. Relaying rumor that a recent battle with the rebellion at Tau Ceti went well, Hoshi plans that – once the war is over – she will return to teaching students in Brazil while Forrest will accept a desk job at Starfleet Headquarters. He, however, explains that the battle was much worse than she has heard; Forrest implies that he is hiding the truth from the rest of the crew. Hoshi advises him to forget about the war and goes back to passionately kissing him.

As Enterprise warps through space, Forrest is making his way through the ship, closely followed by a , when they are ambushed by Archer and MACOs allied with him, including Major Reed in a turbolift and Sergeant . Despite Archer ordering Reed to lock Forrest in the brig, the Major is intent on killing the imprisoned captain. Archer threateningly insists that Forrest be kept alive so Reed ultimately relents.

 is sitting in the bridge's command chair when Archer and his MACOs arrive. Archer seizes control of the bridge and – via a ship-wide communication that is heard by Hoshi Sato, Dr. Phlox and the disfigured Chief Engineer  – he assumes command of the rest of the ship, claiming that Starfleet ordered not only his takeover but also that he direct the ship on a vital, secretive mission into Tholian space. He assures the crew that if their mission is successful, Starfleet will crush the rebellion once and for all. Following the message, Archer tells a suspicious T'Pol that his orders were privately sent to him. He oversees the ship's change of course and orders T'Pol to help with the installation of a stored Suliban cloaking device, as it will be necessary to the mission.

"Enterprise starlog, Captain Jonathan Archer. The crew has accepted the change of command without incident. Chief Engineer Tucker reports we'll have cloaking capability within six hours."

In the captain's ready room, T'Pol reluctantly accepts that Archer is in command. He shows her Zefram Cochrane's shotgun from a century prior, wondering what might have happened if Cochrane had not used it to kill the first Vulcan who set foot on Earth. Reminding T'Pol that she is also Vulcan, Archer asserts his authority. She lets him know that they have likely already entered Tholian-occupied space, as they frequently annex systems outside of their core territory. Archer assigns her to search for a particular warp signature and, just as she is about to leave, he calls her back in with news that he is promoting her to first officer, explaining why he prefers to assign her to that position rather than Reed. Finally dismissed by Archer, T'Pol exits. He meanwhile returns Cochrane's gun to its display.

Later, Archer personally promotes Sergeant Mayweather to acting as the Captain's personal guard. Mayweather starts to congratulate Archer on his successful mutiny but the newly appointed captain cuts him short, followed by snarls from a hungry . Hoshi arrives and Archer dismisses Mayweather. Hoshi admits that she knows Archer didn't receive orders from Starfleet. He shows a curious Hoshi that Forrest is still alive through an image of the brig on his desktop monitor and says the former captain will remain that way as long as Hoshi cooperates. Although she seduces Archer into accepting her continuance as the Captain's woman, she pulls a knife out while they kiss. He disarms her as T'Pol hails him. The Vulcan reports that Enterprise is approaching the sought-after warp signature and Archer warns Hoshi to be "in a better mood" upon his return.

Enterprise drops out of warp, nearing its target: a , manned by a single Tholian. Following a failed plan to tractor onto the enemy craft and a subsequent brief exchange of firepower, Enterprise disables the Tholian ship. Its pilot starts an overload in its reactor but is beamed into Enterprises Decon chamber just as its own ship explodes. Acting on orders from Archer, Dr. Phlox delightedly begins to torture the Tholian by modifying the chamber's atmosphere.

Act Two 

The senior staff gather outside the Decon chamber. Archer is initially startled by the Tholian suddenly appearing. He is interested to know where the Tholians have taken a  vessel they captured. Phlox tortures the prisoner until it admits that Archer's quarry is at an orbital facility in the Vintaak system. The Tholian then starts using its own crystalline structure to transmit a distress signal. Archer lets his senior officers know that he would prefer to keep the alien alive but unconscious until its information is confirmed.

Working with T'Pol on installing the cloak in Engineering, Tucker sees to it that she has a radiation meter from engineering officer , as it will prevent her from absorbing the same kind of delta rays that disfigured him. Discussion turns, much to T'Pol's discomfort, to a past experience wherein Tucker allowed her to relieve pon farr with him. Tucker receives an electric shock from an overload sparking to the cloaking device.

Archer and Reed later inquire into the incident. The captain is insistent that Tucker prioritize the cloak's repair. Reed is suspicious of the overload, while a secretly knowledgeable T'Pol watches, but Tucker objects to Reed's MACOs investigating.

In the brig, Archer demands that Forrest identify the saboteur, believing it was a spy assigned by Admiral , but Forrest claims ignorance. Archer orders Mayweather, on brig duty, to search the captain's quarters for telltale messages from Starfleet. Mayweather complies, ignoring a cautioning of execution from Forrest. Now alone with Archer, Forrest criticizes him of having always lacked ambition. Archer brutalizes Forrest, citing his imprisonment as a sign that he is incorrect. Forrest pleads for Archer to release him, claiming consequences of both freeing him and killing him. Archer throws him against a bulkhead and departs.

In the bridge's situation room, Reed explains to Archer that evidence points to Tucker as being the saboteur.

Tucker is later punished in the agony booth. Through severe pain, Tucker claims he is innocent and threatens Reed for having implicated him but Reed merely teases Tucker in return. Archer suspects Tucker is Admiral Black's spy and, despite Tucker insisting to the contrary, a distrusting Archer directs Reed to continue subjecting Tucker to the agony booth.

Later in the captain's quarters, Archer and Hoshi lie together, clearly having had a sexual encounter. The captain ensures that Hoshi transmitted data to the fleet admiral but only refers to it cryptically, as an "insurance policy." Archer then starts to suspect T'Pol of being the saboteur, finding that she cannot be located by the ship's computer as the overload damaged the internal sensors.

T'Pol meanwhile leads a successful rescue effort to free Forrest from the brig, two Vulcan companions of hers having a brief encounter with Archer, who escapes in a turbolift. Forrest and T'Pol then retake command from the bridge but find that the ship is locked on course, which Archer personally confirms before sarcastically relinquishing command to Forrest.

Act Three 
With Archer having spent ten hours in the agony booth, Phlox remarks to Captain Forrest that he is amazed by Archer's pain threshold but the captain is reluctantly forced to release Archer from the booth. Forrest not only wishes to instead use it on Major Reed but also privately informs Archer that Fleet Admiral  has ordered his release, having been intrigued by the data Archer sent via Hoshi; the captain implies that the data pertained to Archer's plan to search for the captured Terran vessel. A seething Forrest lets Archer know that his betrayal is unforgivable and notifies Archer that he is due to brief the senior staff in an hour.

While Enterprise continues at warp speed, the senior staff are gathered in the briefing room. T'Pol cites the findings of the Vulcan Science Directorate as proof that alternate realities do not exist but Archer says Tholians are a little more open-minded than Vulcans. He continues briefing the senior staff, explaining that – after managing to open an interphasic rift into a parallel universe – the Tholians intentionally lured a ship through from the other side. Archer also reveals that he bought his information from a Humanoid laborer working for the Tholians and shows the other officers some images of the captured ship. The assembled crew members muse over the significance of the craft, which Archer says is not only from another universe but also from about a hundred years into the future. T'Pol strongly objects to the information, fearing it is a trap and reminding Forrest of Archer's crimes, but Forrest insultingly interrupts her – adamant that they will investigate the ship – and instructs Tucker to get the cloak working before he exits.

While working on the cloak in Engineering, Tucker becomes distracted by T'Pol's presence and vents his anger at her for having apparently falsified the evidence that incriminated him earlier. She explains that she seduced him away from engineering before motivating him, by way of a mind meld, to sabotage the cloak himself before using another meld to alter his memory of what had happened. She states that she was duty-bound to help Forrest regain command. Tucker warns that she will regret her actions, although T'Pol dismisses his threat. He calls the bridge and reports that the cloak is ready, so Forrest orders for it to be engaged. The ship at first encounters slight energy fluctuations but then cloaks.

Soon thereafter, T'Pol is at the bridge's science station when Enterprise reaches its destination, in proximity of a gas giant in the Vintaak system. The bridge officers spot the captured ship in a drydock built into a moon of the gas giant. The vessel is the  Federation starship .

Act Four 
T'Pol briefs Archer, Tucker, Reed and Forrest in the situation room, telling them that Defiants systems, even that of life support, are powered down. Those alive aboard the Defiant consist of thirteen non-Humans, including one reptilian. Although Tucker is impressed by the vessel's engineering capabilities, Forrest plans for Archer to lead an assault team to salvage as much as possible from the craft's databanks before destroying the ship, as the captain fears that the region of space is too dangerous due to the Tholian presence. Archer objects to this plan but Forrest shouts him down. Moments after the others leave, Forrest instructs T'Pol to join the assault team, conspiratorially implying that he wants her to ensure Archer dies during the mission.

Wearing environmental suits, the team (now including Sergeant Mayweather) beam into a corridor of the Defiant to find that the Tholians have been gutting the vessel. The team also come across a dead Human security officer lying beside a discarded phaser. Reed offers to hold the weapon but Archer takes it instead, holstering it to his EV suit's pants.

On Enterprise, a sedative that Phlox has been using on the Tholian pilot stops working and the alien begins retransmitting its bodily distress signal. After the signal is detected on the bridge, Forrest contacts Phlox, ordering him to kill the Tholian. Doing so takes time and Phlox becomes impatiently frustrated. He eventually succeeds in destroying the Tholian but its communication has attracted the attention of three Tholian vessels that approach Enterprise and start to hail the ship.

The assault team meanwhile arrive on the Defiants darkened bridge. They find only two deceased officers there, one of whom is a man wearing a command division uniform; Archer assumes he is the captain and T'Pol reports he has a broken neck. With Archer's approval, Tucker begins attempting to repower the vessel.

Four more Tholian ships approach Enterprise and, despite an initial attempt by Forrest to withdraw from the mission, the alien vessels are not only jamming communications between the pair of Starfleet ships but also subsequently create an energy web that surrounds Enterprise. Forrest first tries to fire the ship's weaponry through the web and then maneuver out of it but neither method succeeds; Enterprise is trapped.

Tucker's eventual restoration of power to the Defiants systems enables T'Pol to monitor Enterprises situation.

Moments later, Forrest orders the crew to abandon ship but, much to Hoshi's concern, he chooses to stay behind in the hope that he might be able to buy the survivors more time.

Archer orders that the Defiants weapons and engine systems are brought back on-line and, with the help of Mayweather and Reed, he starts to remove the two dead officers from their positions in front of the command chair.

Enterprise meanwhile launches its complement of escape pods but many are instantly destroyed. Forrest holds on to the helm station of his dying ship, moments before the assault team watch through the Defiants viewscreen as Enterprise explodes.

TO BE CONTINUED...

Log entries 
"Captain's starlog, January 13, 2155: We've left Gorlan Station and have set a course to rendezvous with our assault fleet. Major Reed and the doctor have asked for a few minutes to show me their latest project."
"Enterprise starlog, Captain Jonathan Archer. The crew has accepted the change of command without incident. Chief Engineer Tucker reports we'll have cloaking capability within six hours."

Memorable quotes 
"Live long and prosper."
( shoots the Vulcan captain, killing him)
"Board their ship! Take everything you can!"
 - The Vulcan captain and the grizzled man, on first contact between Humans and Vulcans in the mirror universe

"The booth will be far more effective than our previous disciplinary methods."
"It can stimulate the pain center of virtually any humanoid. A synaptic scan calibrates it for each species."
"They call this progress!"
"There's something to be said for a good, old-fashioned flogging."
 - Reed, Phlox, Archer, and Forrest, discussing the virtues of the latest in torture technology

"Something about... your 'maternal ancestor'."
 - Sato, translating a Tholian insult hurled at "Captain" Archer 

"You don't want to end up like me, do you? I've absorbed enough delta rays to guarantee my grandchildren glow in the dark."
 - Tucker, to T'Pol, on the dangers of delta radiation

"I did you a favor once."
"We agreed never to discuss that."
"And I haven't."
"I'd hardly call it a favor, you enjoyed yourself."
"Several times as I recall. So, how many years is it 'til your pon farr comes around again?"
 - Tucker and T'Pol

"This isn't like you, Jonathan. You never lusted for power and glory. That's why I trusted you at my side all these years – because you have no ambition!"
 - Forrest, to Archer

"The Tholians are a little more open-minded than your people. They detonated a tricobalt warhead here, inside the gravity well of a dead star. The explosion created an interphasic rift. A doorway into another universe."
"A doorway?"
"The rift was unstable. It was too dangerous to send one of their own ships through, so they transmitted a distress call into the opening, hoping to lure a ship from the other side. Their plan worked brilliantly."
 - Archer and Tucker, referring to the past events of 

"The Tholians quantum-dated a piece of the hull. The ship is not only from another universe; it's from another time. About a hundred years into the future. Imagine the technology we can find on that ship. New tactical systems, advanced bio-weapons. Engines that can reach speeds we can only dream of. All of it, ours for the taking!"
 - Archer, on the 

"Will you kindly die?"
 - Phlox, to his Tholian prisoner

Background information

Introductory details
 Depending on counting of episodes in  – in particular, whether "The Menagerie" is counted as a single or double episode (Memory Alpha considers it two, with a first and second part) – this episode can either be considered as being the seven-hundredth live action episode of Star Trek or half of that "episode" (if the term is applied more loosely), with the other half being this installment's conclusion, .
 The title of this episode comes from a passage in the Bible (1 Corinthians 13:12 from the American Standard Version): "For now we see in a mirror, darkly; but then face to face: now I know in part; but then shall I know fully even as also I was fully known." The same verse (in the King James Bible, the relevant text reads "For now we see through a glass, darkly") is quoted by Captain Picard in .
 This episode is both a prequel to  and a sequel to .
 Although  was the first of any Star Trek series in which none of the regular characters appear, this was the first mirror universe episode in which only the regular characters' mirror counterparts are seen. This differs from the mirror universe episodes of TOS and , in which the "Federation Universe" characters travel to the parallel universe (and vice versa). The two-part "In a Mirror, Darkly" story of ENT takes place entirely in the mirror universe, with no crossover of any regular characters (although the Constitution-class Defiant does itself cross over and the mirror Archer has a hallucination of his prime self).
 This episode contains two main elements from : the starship Defiant (whose fate is made known in this episode) and the Tholians. In fact, this episode is the first to depict a Tholian "in the flesh" since the  episode, wherein only the head of a Tholian is shown. The species is revealed in this episode to be six-legged and crystalline in nature.

Story development
A mirror-universe story for Star Trek: Enterprise was originally conceived as one of a couple of ways of bringing William Shatner into the series' fourth season. (Inside the Mirror Episodes, ENT Season 4 DVD special features; ) As he and Paramount were unable to reach an agreement, the plans to have Shatner included in the series were discarded, the initial mirror-universe storyline ultimately being undeveloped. 
 Nevertheless, the series' writing staff still wanted to do an episode set in the mirror universe. (Inside the Mirror Episodes, ENT Season 4 DVD special features; ) The "episode in the Mirror Universe" format, as opposed to the crossovers in other series, was thereafter conceived as a way of allowing the show to visit the mirror universe, while still preserving  as the "obvious" first contact between the two universes. (Inside the Mirror Episodes, ENT Season 4 DVD; Mirror Universe, Part 2, Star Trek: Fan Collective - Alternate Realities DVD special features) Writer Mike Sussman attributed this idea to Executive Producer Manny Coto and remarked, "What was great about an approach where our people weren't crossing over to the mirror universe is that you didn't have any of the moralizing speeches where Archer or somebody waves their finger and lectures these 'bad people' about 'Well, you really ought to try this other way." (Mirror Universe, Part 2, Star Trek: Fan Collective - Alternate Realities DVD special features)

 The Defiant ended up in this story after Mike Sussman had spent years wondering about the ship's destiny, as the vessel mysteriously disappears in "The Tholian Web". The starship was also in the original pitch for an earlier ENT episode that Sussman wrote. This pitch became Season 2's , which also features the Tholians (although only their ships are seen and not they, themselves). Like in this episode, both Archer (albeit the Archer of the series' usual universe) and the Tholians would have been interested in the futuristic Federation starship. However, the effect that the discovery would have on the series' continuity would have been too difficult for the writers to deal with, so the ship was changed to an unrelated, even more futuristic vessel and the original premise was scrapped. When Manny Coto later wanted a mirror-universe episode to be included in Season 4, however, Mike Sussman suddenly realized (following several other ideas for the episode that, for a variety of reasons, had not worked out) that the Defiant could feature in the episode, having not only been pulled into the past but also into the mirror universe. This change of setting freed the writers from continuity concerns, as they could essentially do virtually anything they wanted in the mirror universe without violating canon. (Inside the Mirror Episodes, ENT Season 4 DVD special features)
 Manny Coto subsequently suggested that the story could be a two-parter, although Mike Sussman had only planned what would happen in the first part. (Inside the Mirror Episodes, ENT Season 4 DVD special features) In addition, he had never before written a two-parter and, at the time he wrote this episode, it was not yet known who would be writing its conclusion. (ENT Season 4 DVD audio commentary; Mirror Universe, Part 2, Star Trek: Fan Collective - Alternate Realities DVD special features) Because the second part would definitely be set on the Defiant, however, Sussman wanted to set some things up in this episode for the second part of the story. (Inside the Mirror Episodes, ENT Season 4 DVD; Mirror Universe, Part 2, Star Trek: Fan Collective - Alternate Realities DVD special features) Owing to the fact that the story was his first two-parter, Sussman wanted to do justice to it and tried to invest as much time in its writing as he possibly could. (ENT Season 4 DVD audio commentary)
 During the writing process, Mike Sussman managed to obtain the script of  from Tim Gaskill and read it for the first time. (ENT Season 4 DVD audio commentary)
 One of the first ideas that Mike Sussman had for this episode was that Hoshi Sato would be the captain's woman. Such a dramatic reversal of the character's usual nature was not disputed by anyone involved in the episode's creation. (ENT Season 4 DVD audio commentary)
 Even though the series' team of writers knew, early in the writing process, that they wanted Hoshi to be the captain's woman and Archer to be a beaten-down and paranoid first officer, it was not until later that the team decided what the mirror universe version of "Trip" Tucker would be like. Manny Coto wanted him to be scarred, so the Reeves-Stevens came up with the concept that the scarring was due to the radiation plating involved in Enterprises warp reactor being not quite up to Starfleet specifications. The series' writers then recalled that Fleet Captain Christopher Pike has a disfigurement, due to delta radiation, in "The Menagerie" so they added Trip's facial scarring in this episode, with the intention of it being a small homage to Pike as well as a factor implied as motivating the character of Tucker (whose condition is less severe than Pike's, as Pike was flooded with the radiation while Tucker only received small amounts of it). (ENT Season 4 DVD audio commentary)
 The writers aimed to give Mayweather a more active role in this episode than the character was usually afforded in the series. (ENT Season 4 DVD audio commentary) Author Diane Duane's decision to make the mirror version of Reginald Barclay the personal guard of Mirror Picard – in the non-canon novel Dark Mirror, which Mike Sussman read before writing the script – inspired Sussman to make Mayweather the chief bodyguard for Archer. (Information provided by Mike Sussman) Additionally, it was thought that making him Archer's personal guard would be more fun for the character of Mayweather. (ENT Season 4 DVD audio commentary)
 Similarly, the writers wanted to make the mirror universe T'Pol more ruthless, and logical in a less compassionate and much harder way, than her counterpart in the regular universe. (ENT Season 4 DVD audio commentary)
 Mike Sussman wrote the episode alone over the Christmas  hiatus. He periodically faxed pages to Manny Coto who – although getting married in Venice, at the time – had several phone conversations with Sussman in which Coto talked about his own story suggestions, changes, and notes. Sussman was still writing this episode when the production crew started filming the second part of the two-parter. (ENT Season 4 DVD audio commentary)
 In the initial version of the story, T'Pol was trying to sabotage the cloaking device in order to prevent the mission going ahead. Mike Sussman thought this subplot was too straightforward, however. With Manny Coto's input, the sabotage was changed to being a diversionary act that would enable T'Pol to attain her new motive of disabling the sensors so she could free Forrest. This alteration, which Sussman found made more sense than his initial conception of the story, was made early in the writing process. (ENT Season 4 DVD audio commentary)
 The idea of this episode's teaser, a homage to , was originally suggested to Sussman by Manny Coto. Sussman was immediately impressed by the idea. (ENT Season 4 DVD audio commentary)
 The scene in which Reed and Phlox demonstrate the agony booth was originally scripted without Phlox's inclusion, as Mike Sussman decided only later to have the scene serve as Phlox's introduction in the episode. (ENT Season 4 DVD audio commentary)
 Keeping Captain Forrest alive, during his capture and imprisonment by Archer, represented a slight story problem for Mike Sussman, as he needed Forrest to survive until the episode's conclusion. The involvement of Hoshi Sato allowed Sussman to solve this problem, as Forrest threatens Archer (during the scene in which they are both in the brig) that Hoshi will not forgive him if he kills Forrest. (ENT Season 4 DVD audio commentary)
 One of the biggest problems that Mike Sussman faced in writing this episode was how to explain away Forrest sparing Archer's life, after Forrest regains command of Enterprise. Sussman consequently added the plot point about Archer smuggling fascinating information to the admiral, via Hoshi. (ENT Season 4 DVD audio commentary)
 Another plot problem was how to account for Forrest sending Archer to board the Defiant after Archer had betrayed Forrest. The solution – to end the scene with Forrest privately revealing to T'Pol that the reason was that he wanted her to make sure Archer didn't survive the mission – suddenly occurred to Mike Sussman and made immediate sense to him. (ENT Season 4 DVD audio commentary)
 Mike Sussman originally wanted to save the reveal of the fact that the Defiant was from 100 years into the future until after Archer and his assault team board the vessel. Sussman found himself having to add that fact into Archer's briefing scene, as the ship would otherwise seem too insignificant at that point in the story. (ENT Season 4 DVD audio commentary)
 In an early draft of the script, Archer and his assault team access the Defiant Bridge by climbing through one of two hatches that are on either side of the main viewscreen. Sussman later decided to have the team enter via the turbolift, however. (Information provided by Mike Sussman)
 One of the things that Mike Sussman wanted to set up for this installment's conclusion was that the characters who board the Defiant would be left with no option but to wear TOS uniforms in the story's second part. This is the real reason why Archer and his team are wearing environmental suits when they transport to the Defiant, rather than their regular Terran Empire uniforms. (Inside the Mirror Episodes, ENT Season 4 DVD; Mirror Universe, Part 2, Star Trek: Fan Collective - Alternate Realities DVD special features)
 Mike Sussman found it very hard to write the scenes on Enterprises Bridge during the final battle sequence, as most of the regular characters were off the Bridge and the episode's budget would allow Forrest to speak only with either the ship's computer voice (which was typically inexpensive to hire) or Hoshi Sato; the practicality of hiring an extra to play a speaking officer would have been prohibitively expensive. (ENT Season 4 DVD audio commentary)
 Enterprises prefix of "ISS" was originally present in the script's original draft but got lost in some of the subsequent versions. It is therefore not referenced in episode dialogue but does appear on the starship's hull, thanks to the series' visual effects team. (ENT Season 4 DVD audio commentary)
 The concept of Archer having to use an excuse before he could take control of Enterprise (specifically, his faked orders from Starfleet), was based on Chekov's use of an excuse before trying to take command from Kirk in . (ENT Season 4 DVD audio commentary)
 T'Pol dismisses Tucker threatening her by telling him, "Threats are illogical." These same three words are taken from . In that episode, Sarek says them (adding, "And payment is usually expensive."), after Tellarite ambassador Gav threatens Sarek that he will pay. (ENT Season 4 DVD audio commentary)
 After writing the scene in which Archer personally confirms for Forrest that he has locked Enterprise on course for an unalterable destination, Mike Sussman realized that the plot point was a little reminiscent of Spock locking the Enterprise on course for Talos IV in "The Menagerie". In the episode's audio commentary, Sussman can be heard deciding that the reference was "a subconscious homage." (ENT Season 4 DVD audio commentary)
 Even Mike Sussman was unsure whether the weapons display in Enterprises ready room was originally Forrest's or a result of a redecoration of the room by Archer, following Forrest's capture. (ENT Season 4 DVD audio commentary)
 Although the episode does not clarify the historical accuracy of a reference (made by Archer) to the Vulcans who visited Earth in 2063 as having been an "invasion force," Mike Sussman has since stated that he didn't think the Vulcans had really been sending an invasion force but was sure that Earth's history books had subsequently recorded the Vulcans had been. (ENT Season 4 DVD audio commentary)
 Similarly, Sussman has speculated that Mayweather would have probably been subjected to the agony booth after Archer and Reed, and that T'Pol likely got to her rank of Commander by using the same method she utilized to motivate Tucker, involving two Vulcan mind melds. (ENT Season 4 DVD audio commentary)
 Although the episode also does not definitively establish whether or not Forrest believes Archer's claim of a future starship from an alternate universe (during Archer's briefing scene), Mike Sussman has clarified that he suspects even Forrest doubts Archer's story. (ENT Season 4 DVD audio commentary)
 Mike Sussman found it was fun to write an ENT episode wherein none of the regular characters are friends with one another. (ENT Season 4 DVD audio commentary)

Editing
 One scene that was deemed unnecessary and was ultimately cut was a short sequence showing T'Pol recruiting a Vulcan security officer for her mutiny. (ENT Season 4 DVD audio commentary)
 The original version of the scene wherein Hoshi Sato brings a knife out while kissing Archer was initially longer than in the final version; the scene as originally scripted ended with a shot of Porthos growling. This shot was eventually deleted from an early cut of the episode, owing to the fact that the episode was running a few minutes long. Sussman initially suggested losing the opening scene featuring the agony booth, but was ultimately happy that other cuts allowed the sequence to remain intact. (ENT Season 4 DVD audio commentary)
 Although Sussman believed the editors could have cut the scene where T'Pol explains to Trip how she compiled him to sabotage the cloaking device, the writer found the scene both fun and important to showing how different the mirror T'Pol is from her alternate universe counterpart. (ENT Season 4 DVD audio commentary)
 A panning shot showing the Defiants Bridge becoming energized also had to be cut short, to avoid a continuity glitch. The full version of the shot included the turbolift doors closing but the shot is followed by one in which the doors are open, so the shot was cut to the moment just before the doors begin to shut. Mike Sussman initially hoped the full version of the shot could be kept, but he was still pleased with the final version. (ENT Season 4 DVD audio commentary)

New credits

 This episode, along with the second part, features a completely revised opening credits sequence that chronicles the history of Human warfare and interstellar domination of the Terran Empire.
 The possibility of creating different opening titles for different episodes had been the subject of much discussion by Star Treks writers. Brannon Braga had, at one point, suggested that an alternate title sequence be created for an episode of , although this had not come to pass. (ENT Season 4 DVD audio commentary) Similarly, for , Ronald D. Moore and René Echevarria had initially hoped to complete that episode's Original Series homage by changing the episode's end credits to TOS fonts and theme music (with DS9 background images), but the idea had never gotten far for budgetary reasons, as well as a lack of enthusiasm from the rest of the production staff.  In this case, the alternate credits stemmed from the idea of doing the episode as if it was from the mirror universe version of ENT. (Inside the Mirror Episodes, ENT Season 4 DVD; Mirror Universe, Part 2, Star Trek: Fan Collective - Alternate Realities DVD special features)
 To help deliver the message that we're "not in Kansas anymore," the words "Star Trek: Enterprise" in these titles change from white to black. (Information provided by Mike Sussman)
 The new credits – an amalgam of real world historical footage and motion picture produced clippings – depict World War I fighter aircraft, World War II American troops marching into Paris, a squadron of Stukas, an atomic bomb exploding, aerial carpet bombings, a submarine firing a torpedo, a different moon landing, a T-62 tank, an F-15 Eagle, the destruction of a Klingon Bird-of-Prey, and a battle between Enterprise and the Xindi.
 The alternate credits also include scenes from other Paramount Pictures media, notably the television series , the 1927 silent World War I film  (incidentally, the first motion picture to receive the Academy Award for Best Picture) , and the 1990 feature film . The image of a Boeing B-1B Lancer seen in one of these shots was used at the start of the 2005 film . The image of an energy weapon blasting through a building was repurposed from the  sixth season episode .
 Two scenes showing World War II era German submarines originated from the 2000 Universal Studios war movie ; Universal Studios is the movie distribution partner of Paramount Pictures through United International Pictures.
 Writer Mike Sussman's favorite shot from these titles was that of the  starship firing on the moon. (ENT Season 4 DVD audio commentary)

Sets, props, and wardrobe
 Although it was first thought that this episode's teaser would require part of the Vulcan ship to be rebuilt, long-time production designer Herman Zimmerman had actually saved the mock-up of the craft's lower portion from . The set, having been in storage for almost ten years, was taken out of storage and refurbished before being reused. (ENT Season 4 DVD audio commentary)
 The agony booth's plastic enclosure was a reuse of the quarantine chamber set piece from . (ENT Season 4 DVD audio commentary) In the episode's audio commentary, Tim Gaskill speculates that the booth's interior was likely quite warm, due to the on-set lights as well as the probability that the enclosure would have trapped heat.
 The sickbay aboard the Enterprise of this episode was inspired by a description in the script of , referring to the mirror universe sickbay in that episode as being a "vivisectionist's lab." (ENT Season 4 DVD audio commentary)
 The decision to make this story a two-parter was primarily influenced by the fact that doing so would financially enable the production crew to reconstruct more Constitution-class sets than had been seen in any official Star Trek production since The Original Series. (Inside the Mirror Episodes, ENT Season 4 DVD special features)
 The Defiant corridor set that Archer and his assault team beam into was constructed by Herman Zimmerman and his art department. The set was required to be much more functional than its equivalent from The Original Series, to show the gutting of the ship, including open panels and broken conduits. (ENT Season 4 DVD audio commentary) 

 Although small sections of the TOS bridge had been recreated for  and , this is the first time a full three-quarters version of the famous set stood on a Paramount soundstage since .
 Manny Coto at first had a major concern regarding the age of the set's origin. He explains, "My big concern, of course, was that our heroes would be coming from an Enterprise set that was built in 2005 and designed to look somewhat more sophisticated to a set that was patterned after a  television show, where they didn't have as much money for detail and budget. And so our fear was: Would it look cardboard, and would it look like our heroes had gone to ... a cheesier set, frankly? But it didn't work out that way." (Inside the Mirror Episodes, ENT Season 4 DVD; Mirror Universe, Part 2, Star Trek: Fan Collective - Alternate Realities DVD special features)
 The team who worked on the Defiants reconstruction had spent many years of studying the TOS Bridge, not only for the past official Star Trek episodes that had included portions of the set but also for personal reasons. (Inside the Mirror Episodes, ENT Season 4 DVD special features)
 Production designer Herman Zimmerman and his art department made a few modifications to the Defiant Bridge. The segmented red railing seen in TOS is now perfectly curved. Also, two removable panels are now visible on opposite sides of the main viewscreen, due to the discarded plot point of Archer and his assault team accessing the Bridge by climbing through one of these hatches. (Information provided by Mike Sussman) The Defiant Bridge of this episode also differs from the TOS Bridge because it features subtle movement in its wall-mounted graphics, courtesy of Michael Okuda and his art department, but the graphics are otherwise very similar to those on the Bridge set of The Original Series. (ENT Season 4 DVD audio commentary) Illustrator Doug Drexler says of the graphics, "Those backlit graphics have been sweated over. They really weren't fudged in any way; I studied thousands and thousands of frame grabs." (Inside the Mirror Episodes, ENT Season 4 DVD special features)
 The Defiant helm console and captain's chair had been previously built for a museum attraction. Unlike the command chair on Kirk's bridge, the Defiant captain's chair does not swivel. (It should be noted that the Enterprises command chair does not swivel in , , nor during some of the earliest episodes of the first season of TOS.) Several members of the production staff, including Manny Coto, found it hard to resist an urge to sit in the captain's chair of the reconstructed Bridge set. (Inside the Mirror Episodes, ENT Season 4 DVD special features)
 The production crew paid an extraordinary amount of attention to detail in this episode, even positioning the bodies of the Defiants captain and the redshirt who died, strangling him, exactly where they appear in . Even T'Pol's diagnosis of the dead captain's broken neck is accurate. However, the images on the small screens above the bridge stations do not match with those seen in the Original Series episode.

 Even though Bob Justman, on the authority of Gene Roddenberry, stopped the practice of creating a unique assignment patch for each ship after "The Omega Glory," one was designed for this episode. It is an angled insignia similar to one glimpsed on the registry pennant of TOS starships and in the background of various starbases.
 The shirt worn by the first dead officer that Archer and his team come across was previously used aboard the Enterprise in . Despite the production crew replacing the Enterprise assignment patch with that of the Defiant, a faint outline of the Enterprises arrowhead insignia is still visible on the shirt. (ENT Season 4 DVD audio commentary)
 This episode marks the first appearance of a phaser pistol in the Enterprise series. The prop was an off-the-shelf toy manufactured by Art Asylum, modified with a strip of Velcro to allow it to adhere to Scott Bakula's trousers.
 The Suliban cloaking device was a reuse of the phase cannon model seen in .
 The Terran Empire emblem, which appears on the doors aboard the Enterprise of this episode as well as being worn as an arm patch on Starfleet uniforms of the mirror universe, not only first appeared in  but also used the same globe as the United Earth logo that first appeared in . In this case, the globe emblem was slightly changed from its equivalent in "Mirror, Mirror", to show both of Earth's hemispheres. (ENT Season 4 DVD text commentary)

Cast and characters
 James Cromwell and Cully Fredricksen both appear in this episode (courtesy of footage from ), as alternate versions of their First Contact characters, Zefram Cochrane and the unnamed Vulcan captain respectively. Clearance from Cromwell and Fredricksen was required before the teaser sequence could be given the go-ahead, but the performers graciously accepted the reuse of the footage and did not ask for too much money in return. (ENT Season 4 DVD audio commentary)
 This episode marks the final appearance of Vaughn Armstrong on the series, his regular character of Maxwell Forrest having died in the earlier fourth season episode . Armstrong was extremely pleased that, in this episode, a character he was playing finally "got the girl," in the form of Hoshi Sato. (ENT Season 4 DVD audio commentary)
 According to Mike Sussman, the cast and crew joked that the mirror universe "put the Ho back in Hoshi." (Inside the Mirror Episodes, ENT Season 4 DVD special features)
 On deciding what breed of dog should play the mirror universe Porthos, Mike Sussman suggested a Great Dane. At the episode's production meeting, this suggestion was generally thought to be very funny and insufficiently scary. The other choices were a Pit Bull or a Rottweiler, the latter being ultimately chosen. (ENT Season 4 DVD audio commentary)

Production
 At one point during production, Scott Bakula wondered if it was possible to modify the Terran Empire salute, due to both the cramped conditions aboard Enterprise and the danger that an actor performing the salute – which requires the saluting individual to jut their hand out – could easily collide with an actor nearby. Mike Sussman was asked, by Merri Howard, to visit the set and act as consultant on the salute, to ensure that all actors and extras were performing it correctly. One suggestion was that the actors could minimize the salute to involve only a thump on the chest that, in the final version, precedes the extension of the arm. However, the same action had been used in the parody sci-fi film Galaxy Quest and, when Sussman pointed this out, it was generally agreed that the episode should not mimic the film too closely; consequently, the suggestion was dismissed. The final version of the salute used in this episode differs from the one used in  as the hand is open in the latter example whereas the salute in this episode involves a closed fist. (ENT Season 4 DVD audio commentary)
Jolene Blalock expressed concern over having no lines in the Engineering scene wherein Archer and Reed inquire into Tucker's electric shock as T'Pol quietly watches them. Writer Mike Sussman believed that since Blalock's character had skillfully set up Tucker to take the fall for damaging the cloaking device, it would therefor be smarter of T'Pol to remain silent in order to not give away that she was the conspirator behind the sabotage. (ENT Season 4 DVD audio commentary)
 During the filming of the scene in which Archer tussles with Forrest in the brig, director James L. Conway told Vaughn Armstrong to briefly stick his tongue out amid the conflict. Armstrong thought performing this action was a slightly cheesy moment and he was somewhat embarrassed about it. He later recounted the experience to Tim Gaskill, who can be heard relaying it to Mike Sussman in the episode's audio commentary. (ENT Season 4 DVD audio commentary)
 The filming of the scene wherein Tucker is subjected to the agony booth while Archer interrogates him was very intense, requiring many takes and Connor Trinneer to apparently be writhing in agony inside the booth. Some of the production staff who were present during this experience found it to be upsetting to watch. Neither Mike Sussman nor Tim Gaskill were on the set at this point but both later heard about the intensity of filming the scene. (ENT Season 4 DVD audio commentary)
 Tim Gaskill managed to visit the set to watch the filming of the scene wherein Tucker restores power to the Defiant, lighting up its Bridge. Gaskill later recalled that this experience had been "a great moment." (ENT Season 4 DVD audio commentary)

Modernizing the Tholians
 The process of creating the fleshed-out CGI Tholian was supervised by Dan Curry. (ENT Season 4 DVD audio commentary) Visual effects producer Ronald B. Moore was pleased to be provided with the opportunity of working on designing the Tholians for ENT, having not been given that chance when working on "Future Tense" (due to the fact that the Tholians themselves are never seen in that episode). (Visual Effects Magic, ENT Season 4 DVD special features)
 The visual effects team watched "The Tholian Web" a couple of times to prepare for modernizing the Tholians. (Visual Effects Magic, ENT Season 4 DVD special features) The team's design process included early sketches, some of which were seen by Mike Sussman. (ENT Season 4 DVD audio commentary)
 Ronald B. Moore was at first stumped as to how to approach the task of designing the new Tholian. His usual instinct of modernizing early aliens was to make them as close as possible to the TOS versions while also trying to imagine what the aliens might have been like in The Original Series if that show had had a bigger budget. In this case, even though he thought the Tholian in "The Tholian Web" (Commander Loskene) looks like it's wearing a helmet, Moore instead wanted to make the new Tholian have a crystalline structure. (Visual Effects Magic, ENT Season 4 DVD special features)

 The filming of the CGI Tholian was accomplished using motion-control and required stand-in David Anderson to wear an intricate, black bodysuit that enabled him to be tracked, before the digitally animated Tholian was then made to duplicate his movements, which were subsequently slightly modified. (Visual Effects Magic, ENT Season 4 DVD special features)
 Although the spider-like appearance of the Tholian's modernized exterior might suggest that the Tholians are personally capable of spinning webs like their ships are, Mike Sussman had not considered this until it was pointed out to him by a friend. (ENT Season 4 DVD audio commentary)

Music
 This episode's teaser reuses the theme music of , as written by Jerry Goldsmith.
 The episode also debuted a bombastic,  that was written especially for the two-parter, by prolific Star Trek composer Dennis McCarthy (along with composer Kevin Kiner). This "mirror theme" is used to accompany both the alternate credits sequence, near the start of the episode, and the episode's end credits. When CBS/Paramount syndicated ENT to local television stations starting in late 2005, this theme could frequently be heard in promos for several other episodes of the series, in addition to the two mirror universe episodes. Indirectly referring to the series' usual theme song, Mike Sussman says of the revised theme's success, "We [...] got rid of that, you know, tambourine-slapping theme song for two episodes, which I think a lot of people were happy with." (Mirror Universe, Part 2, Star Trek: Fan Collective - Alternate Realities DVD special features)Continuity
 Phlox is performing a vivisection on what appears to be a Cardassian vole in one scene, perhaps suggesting that the Terran Empire had already encroached on Cardassian space by 2155.
 While trapped in the Tholian web, Enterprise is able to fire weapons through its cloak. However, the cloak appears to momentarily fail a few seconds after Enterprise launches torpedoes, perhaps indicating that the ship has insufficient power for simultaneous use of weapons and cloak.
 It remains unclear how Archer and his assault team got to the Defiant Bridge via turbolift since the ship's power was off. Although not established in the episode, Sussman believed that Tucker's power unit (later used to activate the Bridge Engineering console) could have been used to make the lift operational. (Information provided by Mike Sussman)
 The computer system aboard the Enterprise of this episode has a voice, unlike the Enterprise that is usually featured in the series. The voice is masculine, in common with the computer system aboard the Enterprise of . (ENT Season 4 DVD audio commentary)
 Another commonality between those two episodes is that, in both this episode and , more Vulcans are on the Enterprise than in each episode's respective series; the earlier episode includes a Vulcan bodyguard working for , whereas this episode involves the Vulcan security officers that help T'Pol spring Forrest from the brig. (ENT Season 4 DVD audio commentary)
 The plot point of T'Pol detecting a reptilian aboard the Defiant foreshadows the discovery of a Gorn living on the ship, in the second part of the two-parter. (ENT Season 4 DVD audio commentary)
 Director James L. Conway had previously directed  in , another episode dealing with the mirror universe.
 For the first time in the series, escape pods are used by the Enterprise crew, launched by being ejected through removable panels around the saucer. Even though Mike Sussman was once told that the NX-class Enterprise of the regular universe does not have escape pods, he later implied that he believed the mirror universe setting of this story allows, without breaching continuity, for escape pods to have been assigned to the Enterprise of this episode. (ENT Season 4 DVD audio commentary)
 The web created by the Tholians in this episode differs from the one in "The Tholian Web". In the earlier episode, two Tholian ships connect by reversing into each other and then moving away. In this episode, the beam is emitted from the fore of the vessels. While it took several hours for the Tholians to "spin" their web in the first instance, here it takes a matter of seconds. However, like the Terrans, it could be assumed that the mirror-universe Tholians are more advanced technologically, in their own time period, than their counterparts in the prime universe. The difference in webs might also be explained by the fact that there are only two Tholian ships in the TOS episode, whereas in this episode, there are several. Mike Sussman has commented that the slower method of creating the web would not have served story purposes here. (ENT Season 4 DVD audio commentary)
 In the  episode , a PADD with information about the events of this episode retroactively places them on stardate 0141.7, the earliest stardate yet in any series or film.

Reception
The two-part episode proved to be one of the most popular installments of Enterprise. David Bianculli, the television critic for The New York Daily News, called them "the best hours of Enterprise yet." He wrote, "The biggest treat of this episode, though, is its ability to surprise - and to do so with not only a sense of Trek history, but with a sense of humor." Bianculli added that "by taking a walk on the wild side, Enterprise is being very good by letting its characters be very bad." He rated the episode three-and-a-half out of four stars, and said that it was so much fun that "had they adopted this attitude from the start, Enterprise probably would still be flying missions next season."
In August 2016, Star Trek fans at the 50th anniversary convention in Las Vegas chose "In a Mirror, Darkly" as one of the "Ten Best Star Trek Episodes" of all time, out of more than seven-hundred live-action episodes produced as of that date. 
 Newsweek magazine listed this episode, and its second part, first on its list of "Top 10" Enterprise episodes. (Newsweek: Star Trek - 50 Years on the Enterprise, January/February 2016, p. 82).
 The readers of Star Trek Magazine selected the two-parter as the best episode of Star Trek: Enterprise in their 40th anniversary reader poll ("Who's on Top?," Issue No. 124, 17 November 2005).
 Cinefantastique magazine listed the two-hour episode at #4 on its list of the top ten television episodes of 2005. ("TV: Best of 2005," Cinefantastique 2005 Yearbook Issue, November 30, 2005, p.8).
 Wired named the two-part installment as one of twelve "all-time best Star Trek episodes" available online for binge-watching. 
 The guidebook Star Trek 101 by Terry J. Erdmann and Paula M. Block lists this episode as one of the "Ten Essential Episodes" from Star Trek: Enterprise (p. 262).
 "Everything that was set up in the classic 'Mirror, Mirror' is here and writer Mike Sussman juggles them all expertly," writes IGN.com, awarding the installment five out of five stars. “The actors are obviously having more fun than they've ever had before playing these alternate versions of their regular characters which frankly, have more depth to them than we've seen in the past three-and-a-half years of the series... ['In a Mirror, Darkly'] may be a gimmick episode, but it's a gimmick that works nearly flawlessly and shouldn't be missed.” 
 Brannon Braga was highly impressed by this episode's teaser sequence, later stating, "When I saw that, it was like, 'This should just be a whole season!" 
 This episode was nominated for an Emmy Award in the Outstanding Hairstyling For A Series category.
 A busy box prop from one of the Defiant corridor sets was ultimately auctioned off in week 1 of the It's A Wrap! sale and auction.  The control interfaces for the agony booth from this episode were also sold in the same auction.
 Scott Bakula described the two-parter as a favorite episode of his in an interview with SyFy Wire. 
 John Billingsley and Connor Trinneer were not fans of the two-parter. Billingsley called the episodes "banal" and Trineer described them as "pandering;" while in the same interview, Dominic Keating described them as “good fun.” 
 Linda Park, who had a substantial role in the two-parter as the self-proclaimed Empress Sato, has said: "I think it’s well known that those are my favorite episodes." 
 Following the success of the two-part episode, Sussman contributed the story for a sequel novella, "Age of the Empress," published as part of the first in a series of Mirror Universe anthology trade paperbacks. (Mack, David, et al. Glass Empires - Star Trek: Mirror Universe #1. Pocket Books, 2007).

DVD releases
 As part of the ENT Season 4 DVD.
 As part of the Star Trek: Fan Collective - Alternate Realities collection.

 Links and references 

 Guest Stars 
 Vaughn Armstrong as Maximilian Forrest
 Franc Ross as Grizzled Man

 Uncredited Co-Stars 
 David Anderson as Tholian prisoner
 Jef Ayres as 
 Craig Baxley, Jr. as ISS Enterprise tactical officer
 Caroline Bielskis
 Steve Blalock as Vulcan captain
 Solomon Burke, Jr.
 Dominic Calandra as Enterprise command division officer
 Mickey Cassidy as 
 Mark Correy as 
 James Cromwell as  (archive footage)
 Shawn Crowder as ISS Enterprise MACO
 Evan English
 Cully Fredricksen as Vulcan captain (archive footage)
 Peter Godoy
 Glen Hambly as ISS Enterprise Vulcan officer
 Noelle Hannibal as Vulcan officer (archive footage)
 Scott Hill as ISS Enterprise Vulcan officer
 Dieter Hornemann as Vulcan officer
 Yoshio Iizuka as 
 April Jacobson as Terran officer
 John Jurgens
 Bevin Kaye as Vulcan officer
 Tamara Lee Krinsky (archive footage)
 Ricky Lomax as 
 Andrew MacBeth as 
 Aouri Makhlouf
 James McElroy as MACO bystander
 Louis Ortiz as Vulcan officer (archive footage)
 Cesar Rodriguez
 Rife Sibley as MACO
 Paul Sklar
 Pablo Soriano as Terev
 Cecelia Specht
 John Wan as 
 Eric Warfield as Defiant captain 
 Curtis Wong as Defiant operations lieutenant
 Unknown performers as
 
 
 Defiant operations ensign
 Terran Empire astronaut (opening credits)

 Stunt Double 
 Shawn Crowder as stunt double for Connor Trinneer

 References 
2063, 2155, 2268; ability; agonizer; agony booth; "all hands"; annexation; ; ; boarding party; bomber; Brazil; brig; Calico M950; career; cloaking device; co-conspirator; court martial; dead star; ; delta radiation; dinner; dozen; duty shift; emperor; ; escape pod; Fleet Admiral; flogging; flux coupler; ; gas giant; "glow in the dark"; Gorlan Station; gravity well; Heckler & Koch MP5; insurance policy; internal sensor; invasion force; Kelvin; kiss; looting; Major; maternal ancestor; maximum warp; ; mind meld; mirror universe; mutiny; ; pon farr''; ; progress report; propaganda; reptilian; sabotage; ; sedative; sergeant; sexual encounter; shotgun; status report; Suliban; Tau Ceti; Tellarite; temperature; ; Terran Empire; Terran salute; Terev; Tholian; Tholian space; Tholian web;  (unnamed 1, unnamed 2); tractor emitter; tri-cobalt warhead; Vintaak system; Vulcan; Vulcan Science Directorate

Opening theme references 
2K12 Kub; 75 mm Gun M1916; B-1B Lancer; ; F-5 Tiger II; F-15 Eagle; Fokker D.VII; Junkers Ju 87; M4 Sherman; Project 705; Renault FT; Sopwith Camel; T-62 main battle tank; T-90 tank; Type VII submarine

External links 
 
 
 

cs:In a Mirror, Darkly
de:Die dunkle Seite des Spiegels, Teil I
es:In a Mirror, Darkly, Part I
fr:In a Mirror, Darkly, Part I (épisode)
ja:ENT:暗黒の地球帝国・前編
nl:In a Mirror, Darkly, Deel I
ENT episodes