Twilight (episode)
The effect of a Delphic Expanse anomaly leaves Archer unable to form any new long-term memories. Twelve years later, he wakes up one morning and is stunned to learn the outcome of the Human-Xindi conflict, including the loss of Earth, and the near-annihilation of the Human race.

Summary

Teaser

Jonathan Archer wakes in his quarters in the midst of battle. He rushes to the bridge, demanding to know what's happening. T'Pol, dressed in a command division Starfleet uniform, orders security to take him back to his quarters. Hoshi interrupts both of them, and everyone stares at the viewscreen as the Xindi weapon emerges from a subspace vortex and fires on Earth. The weapon's powerful energy beam boils the oceans, and the surface begins to splinter. As the bridge crew look on in horror, the molten Earth breaks apart and finally explodes.

Act One
Archer wakes in a small house and is puzzled to find himself with visible grey hair, cut in a Vulcan-like style. Emerging into the house he finds T'Pol, who now has far longer hair and addresses him by his first name. Archer is puzzled, as T'Pol insists that he sit down for breakfast, promising the full story. She asks him what the last thing he remembers is, and he replies that they were leaving the command center. T'Pol reveals it has been twelve years since then…

Twelve years earlier, Archer and T'Pol are discussing the upcoming showing of Rosemary's Baby on movie night. Suddenly the ship rocks as it is hit by anomalies. A powerful one hits and runs through the corridor where Archer and T'Pol are. They try to escape but are caught by the wave, and although they escape serious injury T'Pol is trapped by debris. As another wave is about to hit, Archer tries to free T'Pol despite her urging him to leave. Although he is successful and she escapes, Archer is struck by the full force of the anomaly and is left unconscious.

Archer wakes up in sickbay under Phlox's care. Although Archer believes only an hour or so has passed, Phlox reveals he's been there for three days. He explains that the anomaly has infected Archer's hippocampus with interspatial parasites that have left him with , preventing him from forming any long-term memories since the incident. Phlox promises to do everything he can to find a cure.

As a result of his profound disability, Archer was relieved of his command and replaced by T'Pol, who accepted a field commission as a captain in Starfleet. Archer attempts to contribute in some way, but finds that any suggestion he makes is one he'd already put forward. T'Pol feels deeply indebted towards Archer, since he saved her from the anomaly and if he hadn't she would have been the one afflicted with the parasites.  

After the change in command, Enterprise was unable to find the Xindi weapon. When Enterprise drew close to the weapon in 2154, it came under attack by Xindi-Reptilians. Many crewmembers, including Travis Mayweather, died in the assault. The ship also suffered severe damage limiting it to warp 1.7, mainly due to a ramming maneuver T'Pol used to defeat the Reptilians. By the time Enterprise reached the system where it was being constructed, the weapon had already been launched. After destroying Earth, the Xindi continued searching the galaxy, determined to hunt down and kill all Humans. Almost all of Humanity was ruthlessly wiped out. Archer leaves the house, crying, after he hears the bad news.

Act Two
T'Pol explains to Archer that Enterprise, Intrepid, and another two Starfleet starships led a convoy of around 6,000 surviving Humans to Ceti Alpha V. On this remote world, a secret, desolate refugee camp was built to house the remnants of Human society. Enterprise, under the command of Charles Tucker, was stationed in orbit with the remaining Starfleet vessels. Archer retired to the civilian community on the surface. T'Pol was visited by Soval, who offered her the chance to return to service with the Vulcans in order to ensure her safety from the Xindi. T'Pol refuses, criticizing the Vulcan High Command's policy of holding back Earth's warp program and denying humans the technological advances that could have saved them. Enterprise was the only convoy to reach Ceti Alpha V safely, the others being destroyed by the Xindi, at which point T'Pol resigned her Starfleet commission and chose to remain at the refugee camp to care for Archer. For over nine years, this last outpost of Humanity had survived by remaining hidden from the Xindi.

Concluding her story, T'Pol says, "At this point you often wonder if you are the victim of some elaborate deception." Archer admits that the thought did cross his mind. T'Pol makes certain Archer believes her by reminding him about Margaret Mullin, a woman he once asked to marry him. Archer asks how T'Pol could know so intimate a detail, and she explains that their relationship has "evolved."

Shortly after T'Pol explains all this, Phlox arrives from Denobula, also looking a little older. He is ready to try out a revolutionary new treatment for Archer's condition, which he has been developing for nearly a decade. Many of Phlox's colleagues in the medical community were convinced that nothing short of a subspace implosion would destroy the parasites (a treatment which, of course, would also kill the patient). Phlox persevered and developed an alternative but energy-intensive treatment which can target and destroy the parasites without any harm to Archer. With T'Pol, they return to Enterprise, where the warp core will provide the energy necessary for the treatment.

Act Three
Archer receives a hero's welcome aboard his old ship, reuniting with Captain Tucker, Reed and Sato. After the first phase of treatment, Phlox and T'Pol examine records of Archer's brain scans from twelve years ago and realize that the parasites they have eliminated in the present have apparently disappeared from the past as well. If Phlox were to successfully complete the treatment and eliminate all the parasites, then it would be as if the parasites had never existed. This would effectively change history, and Archer would never have suffered from memory loss. Perhaps with Archer in command, Enterprise would have stopped the Xindi weapon, Earth would not have been destroyed, and Humanity would not have been nearly wiped out.

Unfortunately, Archer's treatment is cut short when Enterprise detects a small vessel piloted by Yerdrin Lek, a Yridian spy, near Ceti Alpha. Lek admits to Tucker and Reed that he was paid to keep tabs on Phlox and report if he ever left Denobula, allowing the Xindi to find the last outpost of humanity, and that they will be now on their way to annihilate the last of the surviving Humans. With Enterprises power needed for battle, T'Pol and Phlox cannot complete Archer's treatment. Hoshi reports to Captain Tucker that six Xindi ships are entering the system.

Act Four

The battle begins. At first Enterprise and the other Earth vessels manage to ambush and disable two enemy ships, but ultimately Humanity's last stand does not go well – the Intrepid loses its port nacelle and is forced to withdraw, and Enterprises bridge is destroyed, literally torn from the rest of the ship, killing the bridge officers. 

As Xindi-Reptilian soldiers board the now-adrift starship and start gunning down the crew, Archer, T'Pol and Phlox decide that removing the parasites is the only way they can save humanity now. They manage to reach engineering only to find the equipment needed for the treatment has been damaged. Archer recalls that Phlox said a subspace implosion would destroy the parasites. Desperate and with nothing to lose, Archer, T'Pol, and Phlox feverishly work at the warp core to trigger an implosion. With Xindi soldiers firing around them, Phlox and T'Pol are killed. Archer is also shot, but with his last breath, he manages to push the final lever which initiates the subspace implosion, destroying Enterprise and the parasites...

Archer wakes up in sickbay, not long after he saved T'Pol from the spatial anomaly. Phlox reports that he only suffered a mild concussion, but requests to keep him overnight for observation. T'Pol thanks Archer for saving her from the anomaly despite the risk of a serious injury, and gives him Rosemary's Baby on a PADD since he'll no longer be able to make movie night. After she (at Archer's request) turns down the lights and gives him a extra pillow, Archer jokes she'd make a good nurse.

Memorable quotes
"You'll enjoy it. Rosemary's Baby. It'll scare the hell out of you."
 - Archer explains to T'Pol what will be playing on movie night

"In the corridor, when the anomaly hit, I urged you to leave me behind – if you had, it's likely Id be the one suffering from this… condition."
"Fortunately, I don't take orders from you."
"Captain… I never expressed my gratitude for what you did."
"I suppose there's not much point in thanking me… a few hours from now, I won't remember."
 - T'Pol and an infected Archer

"We've taken nine prisoners, but the brig was only designed for two. I'm not sure what to do with the others."
"Blow 'em out the airlock!"
"Put them in crew quarters under heavy guard."
 - Reed, Tucker, and T'Pol discussing what to do with their Xindi prisoners

"For now, the best I can give you is warp 1.7!"
"We're not going to get very far at that speed."
 - Tucker and Reed, as Reed responds to the status of the engines

"This planet is barely Minshara-class. Maybe we should've picked one with a little more blue and green on it."
 - Tucker, commenting on the desolate state of the planet below

"Our relationship has evolved over the years."
"Exactly how far has it evolved?"
 - T'Pol explains to Archer how close they have become in twelve years

"Did everyone get their own ship while I was gone?"
 - Archer, after learning that Tucker and Reed, as well as T'Pol, had been promoted to captain in his absence

"It couldn't have been easy for you, telling me the same story over and over again for twelve years."
"I don't always tell it in detail."
"I hope I've told you this before, but… I'm very grateful for everything you've done for me."
 - Archer and T'Pol, discussing her role as his caretaker

"Your engineers won't let us continue the captain's treatment!"
"Those were my orders – look, I'd do anything to help the captain, but we've got bigger problems at the moment."
"This may be the only solution to your problems, captain."
"Destroying these parasites is most likely the key to saving Humanity – and Earth."
 - Phlox, Tucker, and T'Pol, after the effects of the treatment has been discovered

"This image was taken a few minutes ago. You can see the region where I eradicated the first cluster of parasites? It's gone in this image as well…This scan was taken over twelve years ago. The cluster has disappeared from all the scans I've taken over the last twelve years – it's as though it never existed at all."
"By destroying the organisms in the present, we appeared to have neutralized them in the past."
"We know they're from another spatial domain. Apparently they also exist outside of time – if we can eliminate all of the parasites, it's possible the captain's infection will never have occurred!"
 - Phlox and T'Pol, explaining their fateful discovery to Captain Tucker

"If the Xindi are on the way, there's very little we can do to stop them."
"Well we can't just run up the white flag."
 - T'Pol and Tucker, after he denies her request

"Our shields are holding. Nice to know they work in combat."
"Remind me to send a thank you note to General Shran."
 - Reed and Tucker, discussing Enterprises deflector shields, previously untested in battle

(Horrified) "The bridge is gone…"
(Realizing there's no one to stop her from treating Archer) "T'Pol to Phlox… meet us in engineering. We're going to finish the procedure."
"We don't have time to worry about parasites right now."
"That's not necessarily true."
 - Archer and T'Pol

"I'm sorry , Captain – the chamber's been damaged."
(Archer initially looks up in horror, before remembering that there was another way) "Didn't you say we could destroy the parasites with a subspace implosion?"
"Yes, but that would…"
"Can we create one?"
"We would have to overload three plasma injectors – that would send a feedback pulse through the reactor."
"You'll destroy the ship!"
"At this point, it won't make much of a difference!"
 - Phlox, Archer and T'Pol

"You two, get to a shuttlepod. They're only after Humans – if this doesn't work out, you'll still have a chance…(the Vulcan and Denobulan exchange a quick glance, and T'Pol walks up to the warp core to render assistance)… That's an order!"
"With all due respect, you were relieved of command."
 - Archer, and T'Pol

"You could've been seriously injured – I told you to leave me behind."
"Fortunately, I don't take orders from you."
 - T'Pol and an uninfected Archer, in the restored timeline

"You know… you'd make a wonderful nurse."
 - Archer to T'Pol, after she got him an extra pillow

Background information

Story and script
According to Mike Sussman, this story was originally pitched as an episode for , with Kathryn Janeway as the afflicted captain, and Chakotay as her caretaker. Sussman commented, "It was my attempt at writing a love story for those two, but I couldn't sell the Voyager producers on the idea. It turned out to work better as an Archer and T'Pol story anyway, with the background of the Xindi war upping the stakes." 
A "Time-line" page in the front of the script explains that the "episode takes place in four different time periods." They are: "The Present" (October, 2153); the "Very Near Future" (April, 2154, approximately six months in the future); the "Near Future" (a year and a half in the future, or mid-2155); and "The Future" (twelve years in the future, 2165). The slugline of each scene in the script includes the specified time period, "EXT. SPACE - ENTERPRISE - VERY NEAR FUTURE (OPTICAL)," for example.
Responding to criticisms of the use of the "reset button" at the end of the episode, Sussman commented, "I wanted Archer and/or T'Pol to take away something from that experience, too – but to me it would have been a cheat to do that. Archer doesn't get 'thrown back in time' when the parasites are destroyed; we as the writers simply decided to cut back to that point of departure where his life had changed. So why would he have remembered future events from an alternate reality that (a) are in an alternate reality and (b) haven't happened yet? That show was set 20 years in the future; say in the real Star Trek universe, Archer is now the first president of the Federation and he's married to T'Pol – we could have just cut back to that and said, 'OK, it's 20 years later, still' we haven't changed the time, but we're back in the proper timeline. Well, that would have been bizarre." 
In selecting Ceti Alpha V as a setting for this episode, Mike Sussman was influenced by the film . The choice of this planet as the location of the last Human colony was something of a "cruel joke" on the part of Sussman. Even if the Human survivors managed to escape detection by the Xindi, their planet will be made uninhabitable in a little over a hundred years when Ceti Alpha VI explodes, as explained in The Wrath of Khan. (Information provided by Mike Sussman)
Enterprise shepherding a "rag-tag fugitive fleet" to a new home after the destruction of Earth was an homage by writer Mike Sussman to . Sussman had read a bootlegged copy of the pilot script for the re-imagined series prior to writing "Twilight". (Information provided by Mike Sussman)
Although not acknowledged in dialogue, Hoshi sports lieutenant's bars on her uniform in the future. She's also carrying a book to give to Archer. In a line deleted from an earlier version of the script, she hands Archer the hardcover and says, "The Vonnegut collection you asked for." When Archer reacts, puzzled, she adds, "I know you don’t remember asking for it... but trust me, you did." Archer responds, "Look forward to reading it... twenty or thirty times." The  reference was an homage to the author of , another story with a time-jumping protagonist, much like Archer in this episode. 
Captain Archer's condition may have been inspired by the real-life story of Henry Molaison. In 1953, in an attempt to cure him of epilepsy, Mr. Molaison had two thirds of his hippocampi, parahippocampal cortices, entorhinal cortices, piriform cortices, and amygdalae removed. From that point on, Molaison (or "H. M.", as he soon became known in medical texts) became unable to commit new facts to long-term memory. For each subsequent day, until his death in 2008, people had to explain to him, like T'Pol does for Archer in this episode, what date it was and what had happened since 1953, including having to break to him the death of his parents. The long-term study of Molaison's case revolutionized the understanding of the organization of Human memory and formed the basis of what we know today on the subject.
The final draft script for "Twilight", revisions of which were submitted on  and , gave the Yridian spy the name of "Yerdrin Lek". Earlier drafts called him "Yedrin Koss", but this was changed because there were already two Star Trek characters with similar names:  host Yedrin Dax and T'Pol's husband Koss. Promotional materials for the episode used the earlier, incorrect name, which became widely disseminated. It is worth noting the character's name is never mentioned in the episode as aired.
 The effect shot of the Intrepid losing its nacelle was not originally scripted. Originally, a line of dialogue was meant to deliver this information; however, the effect was deemed to carry a greater impact to the audience, so it was included in the final edit of this installment.
 Captain Tucker's comment about Enterprises shields, "I think we’re going to find out how much of a beating these new shields can take," was written as a deliberate homage to a line of dialogue from . In that episode, Benjamin Sisko comments about the , "Looks like we're going to find out just how much of a pounding this ship can take." ("Twilight" audio commentary, ENT Season 3 Blu-ray special features)

Production 

 Computer monitors aboard the alternate-timeline Enterprise sport a red, yellow and green color scheme (rather than red, yellow and blue), similar to the computer panels used during the 23rd century, as seen in .
 A scene with an aged Porthos (twelve years older) was shot for the future sequences, but didn't make it into the final show. In the "present" scenes, a scene was cut at movie night where Archer told T'Pol about Porthos being stressed, and that he might benefit from neuropressure.
 Archer's grey hair is actually a trimmed version of one of the early test wigs for Soval. The actors embraced this, theorizing that, after many years of living together on the planet, T'Pol was now cutting Archer's hair, hence the slightly Vulcan style. (Information provided by Mike Sussman).
 In an interview with Star Trek.com during filming, Scott Bakula told the site, "We just started an episode today that's potentially the best script we've had and the best show to date, called "Twilight."

Continuity 
The Earth colony is established on Ceti Alpha V, first mentioned in  as the planet on which Captain James T. Kirk of the  exiles genetic superman Khan Noonien Singh in the prime timeline.
An Earth convoy destroyed in the Mutara system is mentioned by Soval, a reference to the site of the climactic battle between Kirk and Khan, depicted in .
 The final battle establishes that Enterprise had received tactical upgrades, including defensive shields, from "General" Shran, who, in the prime universe, played an invaluable role in saving Earth from the Xindi in  and .
 The object Archer uses to fatally stab a Reptilian soldier is a miniature replica of the Zefram Cochrane statue described by Geordi La Forge in .
 The visual effects team were apparently confused by the time-jumping narrative, as the appearance of Enterprise changes inexplicably at times in the episode. About thirteen minutes into the installment, or "six months in the future" (April, 2154, according to the script), T'Pol rams the ship into a Xindi vessel, severely damaging the starboard nacelle. Chronologically, the next scene in the narrative is the opening sequence, when Enterprise arrives at Earth and sees the planet destroyed by the Xindi superweapon. In this scene, the starboard nacelle and its Bussard collector is  undamaged. The next time Enterprise appears in the timeline, 17 minutes into the episode, the ship is escorting a convoy of Earth vessels to safety. Here, the starboard nacelle appears heavily damaged again, exactly as it appeared after T'Pol rammed the ship. The nacelle is apparently repaired "for good" during the year it takes Enterprise and its convoy to travel to the Ceti Alpha system, as explained by T'Pol to Archer.
 The episode offers no indication as to how the crippled Enterprise, reduced to warp 1.7 speed, was able to reach Earth to witness its destruction by the Xindi weapon.  had previously established that it took Enterprise seven weeks at warp 5 just to reach the border of the Delphic Expanse. Writer Mike Sussman revealed that his original intent was to indicate that Enterprise traversed the distance via Xindi subspace vortex, which would have been visible outside Archer's window in the opening scene. This idea was dropped largely for budgetary reasons; and also to avoid confusing the audience with a visual effect that had yet to be designed or established. In the unaltered prime timeline, Enterprise returned to Earth and stopped the Xindi weapon by "hitching a ride" inside a Xindi-Aquatic cruiser, which used a subspace vortex to make the journey in time. (ENT: Zero Hour)

Reception 
 "Twilight" proved to be one of the most popular episodes of the series with critics and viewers. The installment was chosen as the "#1 Fan Favorite Episode" in a Viewers' Choice poll conducted by UPN during Enterprises final season. It was re-broadcast on 8 April 2005 in that context. 
 The Washington Post noted that "Twilight" was Enterprise's "highest rated episode" in their analysis of ratings from the Internet Movie Database (IMDB) in 2014. 
 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. 260).
 Readers of Star Trek Magazine selected "Twilight" as one of the "Top Five" episodes of the series ("Who's on Top?," Issue No. 124, 17 November 2005).
 Critic Stephanie Lucianovic at , aka "Keckler," said that the episode will "get your Heart of Khan pumping with righteous Trekkie excitement," adding that the producers have "come up with something amazing that is completely, unabashedly, and unreservedly worthy of high praise." She gave the episode a grade of "A+," while her site's readers graded it "A." 
 Reviewer James Michael Kozak on Ain't It Cool News, aka "Hercules Strong," said that the storyline "cribs shamelessly" from a number of episodes in the Star Trek franchise, including , , , and , but that "this [episode] remained just different enough for me to kind of love it." He added that the episode presented the viewer "a very real sense of what is at stake in this bizarre conflict with the Xindi" for the first time, and that he was "moved" by the evolution of T'Pol's relationship with Archer. Kozak gave the episode four out of five stars. 
 "Mike Sussman's script for 'Twilight' is an intriguing piece of work," writes Matthew Kresal at WarpedFactor.com. He adds, "It's also a turning point for Enterprise as a whole and was the first sign of what the series might be capable of. On its own it stands out as one of Star Trek's best alternate timeline episodes and rightfully so." 
 Jamahl Epsicokhan at Jammer's Reviews wrote that the episode had "many familiar elements, but [is] a very solid episode nonetheless." Epsicokhan awarded it three-and-a-half out of four stars, saying the installment "ups the action quotient to literally apocalyptic levels. All the while, it conveys an intimate character story that works in its own right. The Little Character Drama merges with the Big Action Spectacle and it all somehow holds together and seems justified and compelling."
 Writer Darren Mooney at The M0vie Blog.com says that "'Twilight' is a surprisingly affecting love story, one that uses a science-fiction premise to capture a very human situation." He added that, "[Mike] Sussman is a writer with a very clear fascination and engagement with continuity and consistency... ['Twilight'] is a beautiful and thoughtful piece of Star Trek, an absolute triumph." 
 Blogger J.P. Halt at his website Random Musings rated the episode 10/10, writing, "Mike Sussman, who is arguably the show's best writer, has crafted a very smart script."  Halt added: "Overall, this is probably the best 'reset button' episode the Trek franchise ever crafted. It's one of of a very small handful of outstanding Enterprise episodes, and a contender for the series' best."
 "Ex Deus" at TrekWeb gave the episode 9.5 out of 10 stars, saying "Scott Bakula gives one of his best performances as Archer."

DVD releases
 As part of the ENT Season 3 DVD
 As part of the Star Trek: Fan Collective - Alternate Realities

Links and references

Guest Stars 
 Gary Graham as Soval
 Brett Rickaby as Yerdrin Lek

Co-Star 
 Richard Anthony Crenna as Guard

Uncredited Co-Stars 
 Joey Anaya as Xindi-Reptilian soldier
 David Keith Anderson as operations crewman
 Breezy as Porthos
 Dominic Calandra as command lieutenant
 Keith Campbell as command crewman
 Jacob Chambers as Xindi-Reptilian soldier
 Jason Collins as R. Ryan
 Mark Correy as Alex
 Ian Eyre as Xindi-Reptilian soldier
 Duncan K. Fraser as Walsh
 Peter Godoy as command crewman
 Scott Hill as Hutchison
 John Jurgens as Xindi-Reptilian soldier
 Ricky Lomax as W. Woods
 Aouri Makhlouf as sciences crewman
 Marti Matulis as Xindi-Reptilian soldier
 Gil Rosales as operations crewman
 Justin Sundquist as operations crewman
 Ator Tamras as A. Tamras
 Chris Torres as B. Moreno
 Mark Wagner as operations crewman

Stunt Doubles 
 Vince Deadrick, Jr. as
 Stunt double for Scott Bakula
 Stunt double for John Billingsley
 Boni Yanagisawa as stunt double for Jolene Blalock

References 
Air Group Ten; Alpha Centauri; alternate timeline; anomaly; anterograde amnesia; antimatter inducer; antiproton beam; blue; boarding party; boatswain's whistle; buyer; ; Ceti Alpha system; Ceti Alpha V; Ceti Alpha V settlement; chromosphere; classroom; close orbit; Command Council; concussion; convoy; corridor; Delphic Expanse; Denobula; distress call; duranium; Earth; feedback pulse; field commission; flight school; ; garbage scow; general; green; hell; high warp; hippocampus; hour; information dealer; intermediary; interspatial flux; interspatial parasite; Jupiter Station; leader; long-term memory; Martian colonies (Mars); millicochrane; Minshara class; microcellular scan; movie night; ; Mutara sector; Mutara system; nacelle; neurosurgeon; phase cannon; plasma injector; plasma torch; quantum theorist; radiolytic signature; ; reserve power; Rosemary's Baby; Rigelian flamegem; senior officer; sentry probe; shields; ; starboard; subspace buoy; subspace implosion; supply locker; tissue damage; transporter; turbolift; Vega colony; Vulcan; ; Vulcan database; Vulcan High Command; warp coil; white flag; Westgate Avenue; Yridians; Zefram Cochrane's statue

Starship references 
Andorian cruiser (one);  (two);  (two); Denobulan shuttle; ; Intrepid; ; J class (two); ; Rigellian scoutship (two); "Warp Deltas" (two); Xindi-Insectoid starship; Xindi-Reptilian warship; Y class (two); Yridian vessel

Unreferenced material 
Jack Archer

External links 
 
 
 
 

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ENT episodes