Cause and Effect (episode)
The destruction of the Enterprise near a distortion in the space-time continuum causes a temporal causality loop to form, trapping the ship and crew in time and forcing them to relive the events that led to their deaths.

Summary

Teaser 
The  is in dire straits, with the starboard warp nacelle having suffered extreme damage from an impact. As casualty reports flood in and the ship's systems start failing, Commander Riker orders all hands to proceed to escape pods as La Forge tries desperately to shut down the warp engines. At that moment, the nacelle completely blows out, sending the Enterprise into a helpless spin. Data reports that the engine shutdown failed, ejection systems are off-line, and a warp core breach is imminent. As a fire engulfs the bridge, Captain Picard orders all hands to abandon ship. Alas, it is too late, as the Enterprise explodes, killing everybody aboard.

Act One 
Despite its previously depicted destruction, the Enterprise, intact and undamaged, is traveling at impulse through space.
"Captain's log, stardate 45652.1. The Enterprise has entered an area of space known as the Typhon Expanse. We are the first Starfleet vessel to chart this unexplored region."

Data, Riker, Worf, and Dr. Beverly Crusher are in the first officer's quarters to play a game of poker. Data shuffles the cards very fast, and because of his android nature, Riker and Worf question whether Data is truly randomizing the deck. Data deals the cards and Worf has the highest hand. The four officers play and eventually a standoff occurs between Riker and Crusher. Crusher calls Riker's bluff and wins the hand, somehow knowing that she would win. After winning, she is called to sickbay by Nurse Ogawa. Upon arriving at sickbay, La Forge tells her that he is feeling dizzy. Crusher finds that although he has the symptoms of an inner ear infection, there is nothing physical to suggest that he has such an infection. After examining him, she prepares a hypospray of vertazine when she has the odd feeling that she has already performed this examination. La Forge has no recollection of it and suggests that she was talking about another patient but Crusher is insistent that it was La Forge whom she treated. She shrugs off her déjà vu and administers the hypospray. Later that night, she gets ready to go to bed and shortly after she does, she starts to hear a voice and that voice soon becomes many voices, which are completely undecipherable. As Crusher puts the light on, the voices stop and she accidentally breaks her wineglass, which was next to her light switch.

The following morning, the senior staff (except for Worf) are briefing each other on the vast undertaking of charting the Typhon Expanse in the observation lounge. As they are about to return to duty, Dr. Crusher reports the voices that she heard the previous night. The other staff are curious about her report and they are interrupted when Worf reports from the bridge unusual sensor readings in the vicinity of the Enterprise.

The staff return to the bridge, where Worf reports that there is a localized distortion in the space-time continuum. Picard orders Ensign Ro to back the Enterprise away slowly but she can't as the maneuvering thrusters fail to respond. The distortion begins to fluctuate and power levels drop. Counselor Troi warns the captain that they must leave the area immediately.

Data reports that something is emerging from the distortion and an unidentified starship emerges. The ship is on a collision course with the Enterprise, just thirty-six seconds from impact and the helm still fails to respond. There is no response when the Enterprise hails the other ship. Picard asks for suggestions. Riker (standing closely to the left of Data) suggests decompressing the main shuttlebay allowing the explosive reaction to push them clear while Data alternatively suggests using the tractor beam to alter the other ship's trajectory; Picard opts for the latter. The Enterprise emits a tractor beam but it is insufficient as the ship collides with the Enterprises starboard warp nacelle, causing it to explode. The events portrayed earlier repeat themselves and again the Enterprise is destroyed by a warp core breach.

Act Two 
Once again intact, the Enterprise is traveling at impulse through a familiar region of space.
"Captain's log, stardate 45652.1. The Enterprise has entered an area of space known as the Typhon Expanse. We are the first Starfleet vessel to chart this unexplored region."

Data, Riker, Worf, and Dr. Crusher are in Riker's quarters playing a game of poker. Data shuffles the cards very fast and because of his android nature and Riker and Worf question whether Data is truly randomizing the deck. Data deals the cards and after the second card Crusher has the highest hand. Each player bets and as Data is about to deal another round, Riker now feels déjà vu and eyes Crusher, having a strong feeling about the outcome of the game and he folds, telling her that she will call his bluff. Crusher eyes Riker back in surprise and asks him how he knew. Riker replies that he "just had a feeling", as did Dr. Crusher. Crusher is called to sickbay and, upon arriving there, La Forge tells her that he is feeling dizzy. Crusher finds that although he has the symptoms of an inner ear infection, there is no physical evidence of one. After examining him, she prepares a hypospray of vertazine, but she has the odd feeling that she has already performed this examination. When she asks La Forge if she did this examination before, La Forge says he too has the feeling that she has, but they cannot remember when it occurred. Crusher checks the medical logs on La Forge and finds that although La Forge recently had complaints about headaches with his VISOR, he had none regarding dizziness. La Forge suggests that it was déjà vu but it was unlikely, since both of them had the feeling. 

Later that night Crusher is in her quarters getting ready for bed and as she does, she hears whispers becoming louder and more frequent. She gets up and calls Captain Picard and at the same time, breaks her glass which was next to the light switch. In the captain's ready room, Picard and Crusher share their recent feelings of déjà vu; while reading, the captain started to feel as though he had read certain paragraphs before but dismissed it (assuming he must have read that same book years ago). Picard orders a ship-wide diagnostic with a report to be made in the morning. At 0700 hours, the senior staff (except for Worf) discusses the results and finds no anomalous readings in the diagnostic, although Crusher discovers that ten other people aboard the Enterprise heard voices at the same time of the night as she did. Worf interrupts from the bridge and reports that there is a distortion in the spacetime continuum in the vicinity of the Enterprise. The staff returns to the bridge. Picard orders Ro to have the Enterprise back off slowly but maneuvering thrusters fail to respond. The distortion begins to fluctuate as power levels on the ship drop.

Counselor Troi warns Picard that they have to leave now. Data says that something is emerging from the distortion and a starship appears. The ship is on a collision course with the Enterprise, just thirty-six seconds from impact and the helm still fails to respond. There is no response when the Enterprise hails the other ship. Picard asks for suggestions. Riker suggests decompressing the main shuttlebay allowing the explosive reaction to push them clear and Data suggests using the tractor beam to alter the ship's trajectory; Picard opts for the latter. The Enterprise emits a tractor beam but again it is too late – the ship collides with the Enterprises starboard warp nacelle, causing it to explode. The previous events replay themselves once more and again the Enterprise is destroyed by a warp core breach.

Act Three 
The Enterprise is traveling at impulse through space.
"Captain's log, stardate 45652.1. The Enterprise has entered an area of space known as the Typhon Expanse. We are the first Starfleet vessel to chart this unexplored region."

Data, Riker, Worf, and Crusher are in Riker's quarters to play a game of poker. Data shuffles the cards very fast because of his android nature and Riker and Worf question whether Data is truly randomizing the deck. Data deals the first set of cards, face down, and Worf is agitated, having the feeling of having done this before, quoting nIb'poH, the Klingon equivalent of déjà vu. Riker says that they have done this before, last Tuesday for the previous poker night but Worf means déjà vu and Crusher has the same feeling. Data now deals the cards face up and Crusher predicts that she will get a queen; she does. She then predicts that Data will get a four; he does. She then tells Data to deal the cards and she, Riker and Worf are overcome with feelings of déjà vu, flawlessly recalling the order of the cards that would be dealt. They all wonder how they knew. Crusher interrupts the puzzlement and calls sickbay asking if La Forge is present but is told he isn't. La Forge soon arrives in sickbay and Crusher leaves. Picard arrives in sickbay seeing Crusher and La Forge – La Forge's VISOR is being examined with a diagnostic tool while a test is being done on his visual receptors. Crusher asks Picard if he has been experiencing déjà vu as of late; he has, as have many other people aboard the ship. Crusher has foregone running a standard test on La Forge in favor of running an optical diagnostic where the results came back positive for a phase shift in his visual receptors, which caused his dizziness as the phase shift was projecting images that didn't exist. Small distortions were found in the surrounding dekyon field and La Forge's VISOR was converting these distortions into the images that he was seeing, causing his dizziness.

Later that night, Crusher is getting ready for bed (dressed in her uniform) and puts her glass on a table rather than next to the light switch. As she goes to bed, she starts to hear voices again. She immediately gets up, prepared with a medical tricorder and records the voices. She calls La Forge, reporting the voices and La Forge reports that the ship's sensors had recorded something strange as well. As she goes out, her coat hits her glass which falls and breaks. Crusher joins La Forge and Data in main engineering. La Forge reports that there was a distortion in the dekyon field. They analyze Crusher's six-second recording, and Data discovers that there are over one thousand voices, all coming from the crew of the Enterprise.

Act Four 
Crusher calls all of the senior staff (Worf is now present) to the observation lounge early in the morning with a suggestion as to what was causing all of the unusual events that happened recently on the Enterprise.

La Forge reports that the Enterprise has most likely been caught in a temporal causality loop, where they have been repeating events over and over again but they have no knowledge of how many times they have repeated events or how long they have been stuck in the loop. Crusher feels that if La Forge is correct, then the voices that she heard may be "echoes" from previous loops. Picard inquires how the Enterprise may have been caught in the loop. Data hypothesizes, from the recording, that the Enterprise had encountered a disaster so serious that the captain would order all hands to abandon ship and replays three segments of the recording – Worf's report of the distortion, Data's report on the collision course and Picard's call for all hands to abandon ship. The staff are clearly disturbed by what they just heard. La Forge suggests that if the distortion was a temporal distortion then the destruction of the Enterprise may have caused a rupture in the space-time continuum, catching them in the loop. Worf suggests that they reverse course to avoid the disaster, but Riker points out that reversing course could be what causes the disaster. Picard decides that they cannot start second-guessing themselves; he orders them to remain on course. La Forge warns that if the disaster is not averted they will forget everything that they learned in this loop. La Forge and Data suggest modulating a dekyon emission which, if done correctly, would set up a resonance in Data's positronic subprocessors, leaving a message. However the message would have to be very short (a few characters or a word at most) and Data would not know what the message is immediately; it would be more like a post-hypnotic suggestion. Picard orders that the steps be taken to find a way to send a message and dismisses the senior staff.

La Forge, Data, and Crusher are in main engineering where La Forge is making some modifications to the circuitry in Data's head, and he attaches an emitter to Data's right arm. Neither La Forge nor Crusher recall having done this before so they feel encouraged. La Forge tests the modifications and finds an active dekyon field. Red alert is called and the three officers return to the bridge. The distortion is present again and the same events happen like before but this time Data is able to input a message on the emitter on his arm just before the Enterprise is destroyed.

Act Five 
The Enterprise is traveling at impulse through space.
"Captain's log, stardate 45652.1. The Enterprise has entered an area of space known as the Typhon Expanse. We are the first Starfleet vessel to chart this unexplored region."

Data, Riker, Worf, and Crusher are in Riker's quarters playing a game of poker. Data shuffles the cards in his typically fast android fashion and Riker and Worf question whether Data is truly randomizing the deck. Data deals the first set of cards face down – however Worf is agitated – feeling as if he has done this before. Riker says that they did last Tuesday, but Worf means déjà vu – and Crusher reports having the same feeling. As Data is about to deal the next set of cards face up, Crusher attempts to predict the order of the cards (the way she did in the previous loop) but this time they are all threes. Crusher is surprised, as she was certain she knew which cards would be dealt. Worf shared the same surprise and the same conviction. Data deals three more rounds and this time all four officers are dealt three of a kind. They are all surprised with the improbability of what just happened. Crusher is then called to sickbay by Nurse Ogawa. When she arrives at sickbay, La Forge complains of dizziness and she performs an exam and the results came back negative. She then runs an optical scan and calls Captain Picard down (while he experiences his déjà vu while reading), reporting to him her findings as she did previously. La Forge then leaves and returns to engineering. 

Data and La Forge are in main engineering and Data runs a diagnostic on the warp subsystems. When he finishes the diagnostic, the results come up entirely as threes. Data says that he has encountered the number three "an inordinate number of times" in the past two hours. La Forge receives an alarm of a distortion in the dekyon field on Deck 9. Crusher (from her quarters) calls La Forge and reports the voices while La Forge reports the dekyon distortion. Crusher leaves her quarters and heads for engineering. As she leaves, Data and La Forge hear a glass shatter, and after asking if everything is okay, Crusher reports that she is fine and continues on her way.

Some time later, the senior staff is in the observation lounge, half-way through discussing the theory of being caught in the causality loop. La Forge and Data report the many sightings of the number three occurring all over the Enterprise, knowing that it is more than a coincidence. Nothing was wrong with the ship, but a diagnostic revealed that there was a dekyon field modulation in Data's positronic subprocessors. They didn't know what caused it, but La Forge said that if he wanted to send a message, he'd do it in a similar fashion. The staff discuss the significance of the number three. Riker asks that La Forge perform a level 3 diagnostic when they are interrupted by Ensign Ro on the bridge. The staff return to the bridge and once again the distortion is present. As before, Picard orders the Enterprise to back off slowly but maneuvering thrusters fail to respond. The distortion begins to fluctuate and events begin to repeat themselves yet again as the unidentified starship emerges on a collision course. Also as before, Picard asks for suggestions and Riker suggests decompressing the main shuttlebay while Data suggests using the tractor beam. Picard opts for the latter but just before Worf engages the tractor beam, Data's gaze is caught by the sight of Riker's rank pips and the android is struck by a moment of realization. He deduces that using the tractor beam will not succeed and instead follows Riker's suggestion of decompressing the main shuttlebay. The bay door opens with gas violently rushing out, successfully pushing the Enterprise out of the path of the other ship and saving it. 

Power is restored and Picard asks Data what happened. Data speculates that "three" referred to the number of rank insignia found on the collar of Riker's uniform, indicating that his suggestion would be the successful course of action. Red alert is canceled and Picard orders Worf to access a Federation time-base beacon to ascertain how long they have been in the causality loop. The beacon confirms that the Enterprises chronometers are off by 17.4 days and Data has them reset accordingly. The Enterprise is then hailed by the other ship, which the Enterprise identifies as the , a  starship, a class which had been out of service for more than eighty years. The Enterprise opens a channel and the Bozemans Captain Morgan Bateson offers assistance while Picard was going to offer assistance as well. 

Bateson is unfamiliar with the configuration of the Enterprise and he explains that they found a temporal distortion inside the expanse, then the Enterprise suddenly appeared with the Bozeman stuck on a collision course with it. Picard tells Bateson that the Enterprise was caught in a temporal causality loop and suspects that something similar happened to the Bozeman. Bateson dismisses Picard's suggestion, claiming that the Bozeman left starbase only three weeks previously, but when Captain Picard asks Bateson what the year is, Bateson replies saying that it is 2278. Realizing the Bozeman has been thrust a full ninety years into the future, Picard suggests that Bateson should beam aboard the Enterprise as there is much to discuss.

Memorable quotes 
"All hands abandon ship! Repeat: all hands abandon…"
- Picard, every time just before the Enterprise explodes and the loop resets

"Still no help for the Klingon."
- Data, dealing cards in one iteration of poker games

"My Aunt  cured a lot of sleepless nights with this steamed milk."
- Picard, sharing a milk toddy with Crusher

"Sometimes I wonder if he's stacking the deck."
"I assure you, commander, the cards have been sufficiently randomized."
"I hope so."
- Riker, Data, and Worf, starting poker (many times)

"I am experiencing nIb'poH, the feeling I have done this before."
"Yeah, last Tuesday night."
"That is not what I mean."
"I've been having the same feeling."
- Worf, Riker, and Crusher

"How'd you know I was bluffing?"
"I just had a feeling."
"I guess it's better to be lucky than good."
"It's the way your left eyebrow raises when you're bluffing." (Riker looks shocked) "Just kidding, commander."
- Riker and Crusher, playing poker

"I'd like to run an optical diagnostic."
"For an ear infection?"
 - Crusher and La Forge"This is highly improbable."
- Data, after Crusher, Worf, and Riker successfully predict ten successive deals

"This is going to sound pretty wild."
- La Forge, before explaining what's causing the déjà vu

"Must be déjà vu."
"Both of us? About the same thing?"
 - La Forge and Crusher, believing she has treated him for dizziness from his VISOR before despite evidence to the contrary

"Back us off, ensign. Nice and slow."
 - Picard, to Ro (many times)

"Somehow we've entered what seems to be a temporal causality loop. We think we're stuck in a specific fragment in time and that we've been repeating that same fragment over and over."
"Is this what's causing our déjà vu?"
"Yes, but it's more than that. In déjà vu, you only think you're repeating events. We actually are."
"Our theory is this: every time the loop begins again, everything resets itself and starts all over. We don't remember anything that happened before, so each time we go through the loop, we think it's the first."
- La Forge, Troi, and Crusher, as La Forge explains the nature of the temporal causality loop

"To date, we have encountered 2,085 conspicuous examples of the number three."
 - Data, on the odd occurrences of the number of three

"The tractor beam will not be successful. I am decompressing the main shuttlebay. "
 - Data, determining the significance of the number three by following Riker's suggestion 

"Captain… do you know what year this is?"
"Of course I do – it's 2278."
(pause)
"Perhaps you should beam aboard our ship. There's something we need to discuss."
 - Picard to Bateson' Background information 
 Production history 
 Final draft script:  
 Production meeting: 7 January 1992
 Filmed: 15 January 1992 – 23 January 1992
 Second unit insert footage filmed: 
 More second unit insert footage filmed: 21 February 1992
 Premiere airdate: 
 First UK airdate: 

 Story and script 
 Writer Brannon Braga came up with the story of this episode while thinking of ways to avoid standard time travel cliches. "I love time travel stories and I don't know who doesn't. We wanted to do a time travel story that had never been done before," Braga recalled. "Being trapped in a time loop is one I've never seen before." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 241)
 Braga noted that while time loops are often associated with the film , the episode was written and aired before the movie. (Star Trek: The Next Generation 365, p. 249)
 The story was still missing some elements. According to Braga, "I came up with the poker game while I was eating pancakes and pouring syrup. I had no idea how it happened – because it was before the sugar rush. I knew then that the poker game would somehow be utilized for once, and lay it in so the viewer thinks it's just a poker game and it turns out to be the key to saving their entire existence." Ronald D. Moore added, "The poker games for a while was the cliche padding. If the show was short, it was time to write a poker game. Because we had written it so much, we stayed away from it and now it got used for a reason." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 241)
 Initially, Riker was going to win the hand in the final loop with three aces, as an additional indicator that Riker's suggestion should be followed. Rick Berman nixed the idea, arguing that Data could program in "three", but not give Riker three aces. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 241)
 Due to the nature of the episode, the production staff were careful to make each iteration of the loop unique. Braga commented, "In a way, doing the same scenes over was comforting; it was fun to come up with different takes and to think how I could get that glass to break each time. It wasn't until I got to the final draft that I thought to have the glass break over the intercom on that final loop through. So it was finding those little nuggets and pathways and weave through as we were structuring it. That was a terrific challenge." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 241)
 Taking the decision to incorporate the Enterprises destruction as the climax of each time loop enabled Braga to begin the show with, as he described it, "the ultimate teaser." ()
 Herb Wright noted, "It's a helluva challenge because when the audience has seen it once and you show it to them the second time, the temptation for them is to jam the button on the remote. The challenge is how do you keep them excited, motivated and involved and wondering what the fuck is going on. And in the teaser you're starting off and you've destroyed the ship so if that isn't going to get you to tune back in, I don't know what will." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 242)

 Production 

 Director Jonathan Frakes recalled, "When I got the script to 'Cause and Effect', I thought it was joke from Brannon Braga. I read Act One. I read Act Two. I read Act Three. I read Act Four. I read Act Five. And I said, 'You guys are screwing with me! C'mon!" (Star Trek: The Next Generation 365, p. 249)
 To ensure that the episode would not be misinterpreted as a clip show, Rick Berman instructed Frakes not to reuse any footage and ensure every loop was filmed in a different way. As such, some of the scenes in this episode were shot using multiple cameras in order to prevent having to shoot the same shot twice at different angles. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 242) Frakes recalled that it was a great challenge, particularly for scenes set on the bridge. "I'd watched a lot of directors by then, and directed a few episodes, so I knew all the possible bridge angles – and I think I used all of them." (Star Trek: The Next Generation 365, p. 249)
 The TNG staff wanted Kirstie Alley, who played Kelsey Grammer's Cheers co-star , to reprise her role as Saavik as the female bridge officer standing next to Captain Bateson on the Bozeman, but scheduling conflicts prevented this from happening. ()
 The production meeting for this episode took place on Tuesday .
 "Cause and Effect" was filmed between Wednesday  and Thursday  on Paramount Stage 8 and Paramount Stage 9. Second unit inserts were filmed on Friday  on Paramount Stage 8 and on Friday  on Paramount Stage 9 and Paramount Stage 10.

 Visual effects 

 Originally, the USS Bozeman was going to be a -era studio model of a  starship, and co-producer Ronald D. Moore, a fan of The Original Series, even went so far as suggesting constructing a TOS-era bridge set for it. () These plans were abandoned due to the costs of creating the necessary ship, props, and costumes. The ship was changed to the , a slight modification of the  miniature, with sets and costumes reused from . (; Star Trek: The Next Generation 365, p. 248) Therefore, the existing Miranda-class model was reused, with several add-ons to give it a different appearance. The modifications were designed by Greg Jein and Mike Okuda. The class was named for . () Okuda made use of the fan-produced Ships of the Star Fleet, Volume One (pp. 84-85) to make annotations on one of the blueprints for the adjustments, eventually seen on screen. Subsequent episodes of this and other series – , DS9's , VOY's , and ENT's  – included recreations of sets and costumes from The Original Series-era.
 For this episode, it was felt that the special occasion of the Enterprise-D's destruction warranted a more realistic and impressive explosion. At the time, the standard technique was to superimpose footage of an explosion over stock footage of a physical studio model of the ship in post-production. In this case, four break-away models were filled up with pyrotechnics, and blown up while shooting from multiple angles. Typically, the debris of such models was discarded after use, but in this case the debris was gathered up on a hunch by Effects Supervisor Gary Hutzel. Hutzel recalled, "[W]e blew up a model for the Enterprise, by dropping it from the ceiling of the sound stage toward a high speed camera while timed charges went off to blow it up in mid-air. I went around with a cardboard box and picked up all the pieces of the model I could find, because I knew they would come in handy someday." The debris was later reused for the destruction of another Galaxy-class vessel, the , in the DS9 episode . (Cinefantastique, Vol. 26, issue 6/Vol. 26, issue 1, p. 109)

 This is the only episode where the Galaxy-class main shuttlebay was featured. Ed Miarecki's company, Science Fiction Modelmaking Associates, was contracted to construct a maquette of the bay. "This set miniature, built in five days, featured a hangar door, which worked like a roll-top desk, and was powered by a cordless electric drill. The two Shuttlecraft in the scene were named for the shows producers, 'Berman' and 'Pillar' [sic]."  Miarecki also created three more tiny Type 6 shuttlecraft and one more Type 15 shuttlepod to go with his maquette.  Despite being a significant feature of the Galaxy-class, the maquette, built around a wooden frame, never made another appearance. The maquette, measuring 9×48×57 inches was eventually listed as  in the It's A Wrap! sale and auction where it sold for US$3,050 on 17 February 2008. 
 A  large nacelle model was also created for the episode. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 242; )

 Continuity 
 This is the third episode in which we see a  starship destroyed, namely, the Enterprise-D.
 Alyssa Ogawa's last name is first mentioned in this episode. Her first name was established in .
 Picard's Aunt  was previously mentioned in , where he gave Admiral Kennelly her prescription for the common cold: ginger tea with honey. Here, he gives Beverly Crusher her recipe for warm milk with nutmeg. Crusher passes on the recipe to Riker in the episode  (although she must have re-learned it at another time, since Picard doesn't share it with her during the final loop).
 The Bozemans "era" of 2278 would be set halfway between the events seen in  and . The wardrobe of Captain Bateson also establishes that Starfleet had switched to the red jacket uniform at least seven years before the "first" time the uniform was seen in .
 The Bozeman was later referenced in the TNG series finale , , and .
 Picard's line "We can't afford to start second guessing ourselves. We should stay on this course until we have reason to change it," is repeated almost verbatim by Deanna Troi in "All Good Things…". She specifically says, "I don't think we can start second guessing ourselves. I think we have to proceed normally and deal with each situation as it occurs."
 This is the first reference to ejecting the warp core; while it is mentioned many more times, the procedure was not seen on screen until , which marked the first of several times the  ejected its warp core. The  ejected its core in , as did the  in  and the  in .
This is the first episode to feature Ensign Ro's new hairstyle.

Reception
Brannon Braga commented that this episode is one of the most popular episodes he wrote personally. ("Departmental Briefing Year Five" ("Cause and Effect"), TNG Season 5 DVD special feature)
Ronald D. Moore thought that it was a "neat episode" with an unbeatable teaser. He also praised director Jonathan Frakes. "Each time through the loop has a different feel, a different nuance, a different look. I think he did a wonderful job on making it an interesting show." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 241)
During the episode's initial broadcast, many local affiliates were inundated with phone calls from viewers who believed that something was wrong with the broadcast, having not paid close attention and believing that footage was simply being repeated. Writer Brannon Braga noted that viewers at the time were much less comfortable with unorthodox structures. ("Requiem - A Remembrance of Star Trek: The Next Generation" ("Part 2: The Needs of the Few"), TNG Season 5 Blu-ray special feature)
A mission report for this episode, by John Sayers, was published in .

Apocrypha
Captain Bateson and the crew of the Bozeman go on to play a major role in the  Ship of the Line.

Video and DVD releases
Original UK VHS release (two-episode tapes, CIC Video): Volume 59, 
In the UK video collection Star Trek: The Next Generation - 10th Anniversary Collector's Edition under the "Ensemble Cast" section, 
 UK re-release (three-episode tapes, Paramount Home Entertainment): Volume 5.6, 
 As part of the TNG Season 5 DVD collection
As part of the Star Trek: Fan Collective - Time Travel collection
As part of The Best of Star Trek: The Next Generation, Volume 2 DVD collection

Links and references
Starring
Patrick Stewart as Capt. Jean-Luc Picard
Jonathan Frakes as Cmdr. William Riker

Also starring
LeVar Burton as Lt. Cmdr. Geordi La Forge
Michael Dorn as Lt. Worf
Gates McFadden as Dr. Beverly Crusher
Marina Sirtis as Counselor Deanna Troi
Brent Spiner as Lt. Commander Data

Guest stars 
Michelle Forbes as Ro Laren
Patti Yasutake as Alyssa Ogawa
And
Kelsey Grammer as Captain Bateson

Uncredited co-stars
Rachen Assapiomonwait as 
Michael Braveheart as Martinez
Debbie David as Russell
Tracee Lee Cocco as Jae
Ericson as Bozeman crewmember or Bozeman lieutenant
Eben Ham as operations division ensign
 as Bozeman crewmember or Bozeman lieutenant
 Michael Moorehead as science division ensign
 as Bozeman crewmember or Bozeman lieutenant
Victor Sein as Bozeman crewmember
John Tampoya as operations division ensign
Mikki Val as operations division officer
Christina Wegler Miles as command division ensign

 Stand-ins and photo doubles
David Keith Anderson – stand-in and photo double for LeVar Burton
Patty Davis – stand-in for Michelle Forbes
Melba Gonzalez – stand-in for Marina Sirtis

 – stand-in for Jonathan Frakes
Nora Leonhardt – stand-in for Marina Sirtis
Tim McCormack – stand-in for Brent Spiner and Kelsey Grammer
Lorine Mendell – stand-in for Gates McFadden
Richard Sarstedt – stand-in for Jonathan Frakes
Dennis Tracy – stand-in for Patrick Stewart
Guy Vardaman – stand-in and photo double for Brent Spiner
James Washington – stand-in for Michael Dorn

References
2278; 2335; 2353; 2357; 47; ; acoustic energy; ; African Confederation; Berman; ; casualty report; catwalk; chronometer; collision course; common cold; damage report; dealer; deja vu; dekyon; dizziness; dozen; drive plasma; ear infection; escape pod; evasive maneuvers; explosive decompression; eyebrow; Federation; ; Galaxy class decks; gravitron polarimeter; headache; inertial damper; insomnia; ; Klingon; Klingonese; level 2 diagnostic; level 3 diagnostic; main shuttlebay; ; milk toddy; Mogadishu; numeral; nutmeg; optical diagnostic; paragraph; particle accelerator; patient; phase shift; phenomenon; Piller''; plasma; poker; positronic net; premonition; ; rank insignia; red alert; senior officer; sensor log; Somalia; ; Starfleet Academy; stellar dynamics lab; subspace scan; temporal causality loop; time-base beacon; tricorder; Typhon Expanse; unnamed starbase; vertazine; VISOR; visual receptor; warp core breach; warp core ejection system; warp field generator; warp nacelle

External links

de:Déjà Vu
es:Cause and Effect
fr:Cause and Effect (épisode)
ja:恐怖の宇宙時間連続体（エピソード）
nl:Cause and Effect
pl:Cause and Effect
TNG episodes