(written from a Production point of view)
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.
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.
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 anterograde amnesia, preventing him from forming any long-term memories since the incident. Phlox promises to do everything he can to find a cure.
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.
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, having felt an intense obligation to care for him since he saved her from the anomaly, an action which resulted in his disability. 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.
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 Enterprise's 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.
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 Enterprise's 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 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 the parasites in his brain (and Enterprise with them).
In 2153 of the new timeline, Archer wakes up in sickbay after saving T'Pol from the spatial anomaly. Although Archer suffered a concussion, Phlox expects a full recovery.
"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 I'd 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
- - Reed and Tucker, discussing Enterprise's 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
Story and script
- According to Mike Sussman, this story was originally pitched as an episode for Star Trek: Voyager, 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." 
- 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 Star Trek II: The Wrath of Khan. 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 Battlestar Galactica. Sussman had read a bootlegged copy of the pilot script for the re-imagined series prior to writing "Twilight". (Information provided by Mike Sussman)
- Captain Archer's condition was probably 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 8 September 2003 and 6 November 2003, 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: Dax 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 Enterprise's 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 DS9: "The Way of the Warrior". In that episode, Benjamin Sisko comments about the USS Defiant, "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)
- 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 Star Trek: The Original Series.
- 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 addition to referencing Star Trek II: The Wrath of Khan, this episode references TOS: "Space Seed", in which Captain James T. Kirk of the USS Enterprise exiles Khan Noonien Singh on Ceti Alpha V.
- An Earth convoy destroyed in the Mutara system is mentioned by Soval, a reference to the site of a battle between Kirk and Khan, also depicted in The Wrath of Khan.
- The battle scene establishes that Enterprise had received tactical advancements from Shran – who, in the prime universe, later plays an invaluable role in preventing the events of this episode from ever taking place, as portrayed in ENT: "Proving Ground" and "Zero Hour".
- 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 Star Trek: First Contact.
- The episode offers no clue 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. "The Expanse" had previously established that it took Enterprise seven weeks at warp 5 just to reach the border of the Delphic Expanse. Producer Mike Sussman revealed, however, that Enterprise was originally intended to traverse the distance quickly via a Xindi subspace vortex, but this plan was dropped.
- This episode was chosen as the #1 fan favorite in an online poll conducted by UPN prior to the final six episodes of the series airing. It was re-broadcast on 8 April 2005 in that context.
- The book 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.
Links and references
- Scott Bakula as Jonathan Archer
- John Billingsley as Phlox
- Jolene Blalock as T'Pol
- Dominic Keating as Malcolm Reed
- Anthony Montgomery as Travis Mayweather
- Linda Park as Hoshi Sato
- Connor Trinneer as Charles Tucker III
- 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 sciences ensign
- Chris Torres as B. Moreno
- Mark Aaron Wagner as operations crewman
- Vince Deadrick, Jr. as
- Boni Yanagisawa as stunt double for Jolene Blalock
Air Group Ten; Alpha Centauri; alternate timeline; anomaly; anterograde amnesia; antimatter inducer; antiproton beam; blue; boarding party; boatswain's whistle; buyer; caretaker; 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; Forrest, Maxwell; garbage scow; general; green; hell; high warp; hippocampus; hour; information dealer; intermediary; interspatial flux; interspatial parasite; Jupiter Station; long-term memory; Martian colonies (Mars); millicochrane; Minshara class; microcellular scan; movie night; Mullin, Margaret; Mutara sector; Mutara system; nacelle; neurosurgeon; phase cannon; plasma injector; plasma torch; quantum theorist; radiolytic signature; Ramirez; reserve power; Rosemary's Baby; Rigelian flamegem; senior officer; sentry probe; shields; Shran, Thy'lek; starboard; subspace buoy; subspace implosion; supply locker; tissue damage; transporter; turbolift; Vega colony; Vulcan; Vulcan; Vulcan database; Vulcan High Command; warp coil; white flag; Westgate Avenue; Yridians; Zefram Cochrane's statue
Andorian cruiser (one); Antares-class (two); Arctic One-type (two); Denobulan shuttle; Enterprise NX-01; Intrepid; Intrepid-type; J class (two); NX-class; Rigellian scoutship (two); "Warp Deltas" (two); Xindi-Insectoid starship; Xindi-Reptilian warship; Y class (two); Yridian vessel
- "Twilight" at StarTrek.com, the official Star Trek website
- "Twilight" at Memory Beta, the wiki for licensed Star Trek works
- "Twilight" at Wikipedia
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