Time's Arrow, Part II (episode)

Trapped in 19th century San Francisco, the crew of the Enterprise must locate Data and prevent his death while stopping the Devidians from destroying Earth's history. (Season premiere)
== Summary ==
=== Teaser ===
The year is 1893 and Samuel Clemens is walking down a street in San Francisco, California with a young reporter in tow writing down much of what Clemens is saying on a notepad while he discusses time travel. He expresses his belief that there are people from the future, "right here in San Francisco." Their discussion ends when Clemens sees Lt. Cmdr. Data emerge from a building nearby and begins walking up the street. As he follows Data, they unknowingly pass a woman walking with a man who is carrying a walking stick with the head of a snake on it.
=== Act One ===
Commander Riker and Dr. Crusher are in a makeshift morgue somewhere in San Francisco in 1893. Crusher is dressed in a black period dress with an elaborately decorated hat while Riker is dressed as a police officer. Riker mentions that the morgue is the location of all the cholera victims. Crusher expresses her surprise at so many people dying of cholera because it "just isn't that virulent." She scans a body with her medical tricorder and finds that the victim's entire nervous system has been depleted of electro-chemical energy. She determines that a number of the victims died because their neural energy was drained, not because of cholera. Riker asks where the aliens from Devidia II with a taste for Human neural energy would go to get a supply. Crusher suggests that they would go to a time when there were epidemics and plagues and use that as a cover to murder Humans for their neural energy.
Later, in a rented apartment, Crusher explains her findings to Captain Picard, Lt. Cmdr. La Forge and Counselor Troi. Riker adds that they found triolic activity in the bodies that had to have come from the Devidians. La Forge suggests that they may be able to create an "alien alarm system" to alert them to the presence of the Devidians. He adds that he has been unsuccessful in contacting Data yet, though his tricorder is broadcasting on all frequencies that Data can sense with his positronic subprocessors. They are interrupted by a knock at the door and a shrill voice shouting for "Mister Pickerd."
Mrs. Carmichael enters demanding the weekly rent. She is upset because it is one o'clock on Thursday and the rent is due at one o'clock on Wednesday. Picard explains that he and his theater troupe are rehearsing for their upcoming production of A Midsummer Night's Dream and that they have played to packed houses in London, Paris, and Milan. He promises her the rent in full with a bonus but she tells him no, she'll have her rent "tomorrow, or you'll be out performing on the street!"
At the Hotel Brian, the bellboy, Jack, lets Clemens into Data's room. Clemens says he is looking for a letter of intent, but he is really just snooping. Jack takes the opportunity to ask Clemens if he'll write his life's story. Clemens tells him, "No one is more qualified to write your story than you are." Clemens encourages him to follow his dreams and go to Alaska. Jack agrees and vows to do it and reveals his full name to be Jack London. He leaves Clemens alone in Data's room. Clemens walks over to a device on Data's desk and removes a piece of it. The device stops functioning just as he hears a noise from the hall. He quickly hides in the wardrobe closet.
Data and Guinan enter the room. She explains that Data will not be able to get into the cavern under the city because the only entrance is in the middle of the Presidio located on an Army base. Data tells her he has full confidence in her persuasive abilities. She finally agrees to help him gain entrance when he notices that the transceiver assembly has been removed from his device. He explains that without it, he will be unable to track the time shifts. Guinan says that she believes Clemens is behind the missing piece because he has been stalking her lately and asking her questions. Data tells her that, if so, he must be warned that prolonged exposure to the piece would be toxic to Human tissue. An unexpected noise, quite like a transceiver assembly being dropped inside a closet, leads them to the wardrobe where they discover Clemens hiding.
=== Act Two ===
Data picks up the transceiver from the floor of the wardrobe as Clemens wipes his hands with a handkerchief. Clemens emerges from the closet as Guinan scolds him for snooping. Clemens is instantly indignant and directs shame at both Data and Guinan. He says his friend Ches Whitley in the county assayer's office has told him that Data claims to be a geological engineer interested in mining operations in the 1850s. He goes on to tell Data many of the other places he's visited recently. Clemens then asks about the device on the desk and whether it has anything to do with time shifts. Data explains that a time shift is a gearing device he has invented for the horseless carriage. Clemens is agitated at the answer and tells Data that he knows he's come to "this century, and brought your infernal technology with you" and that he's up to no good. Guinan interrupts and tells Clemens to mind his own business and leave. Clemens rebuts that it is his business and the business of all Humanity to stop them from whatever they are doing, then he leaves.
In a ward of the Sisters of Hope Infirmary, Picard is reassembling a gas lamp when he is questioned by a doctor. Picard explains that he is replacing the burner with a safer version in case of an earthquake. The doctor tells Picard there has not been an earthquake in San Francisco for thirty years and dismisses him. He walks over to his nurse and tells her (a disguised Dr. Crusher with a tricorder in hand) that he is leaving. Crusher hides the device in her apron and the doctor leaves. Across the room, La Forge says he can see an afterimage of triolic waves by a bed. Crusher says a man just died in that bed the previous night. Troi offers that another patient was complaining about a strange doctor and nurse near that bed and perhaps they're still in the building. La Forge and Troi leave as Crusher tends to a coughing patient.
The device that Picard planted on the lamp begins to flash and Crusher's tricorder makes an alarm noise. She turns to see a doctor in a tall hat and a nurse in a dark cape standing nearby. She activates her combadge and approaches them. She asks the doctor if he needs any help and remarks that his cane is interesting. The nurse aims her bag at Crusher just as Riker, La Forge and Picard enter with Troi close behind. La Forge grabs the cane and knocks the Devidian down on a bed. He gets back up and Riker shoots him with a phaser but he is unaffected. The man turns to his companion and they vanish.
Just then, Data's device records the time shift. He consults a map and hurriedly leaves the room.
Back in the infirmary, a police officer arrives and asks Riker what is going on. Riker is unable to convince him to let them leave and the officer confiscates the cane from La Forge. He tells the group to come with him for questioning, and Riker remarks that he has the "utmost respect for the law" just before he knocks the policeman to the ground and takes the cane. The group then rush out of the room.
They leave the hospital and see Data driving a carriage toward them. He stops and they all get into the carriage. Three police officers run toward them as the galloping horses take them away.
=== Act Three ===
Back in the apartment, La Forge supposes that if he tunes a phaser to the approximate frequency of triolic waves and hit the cane with a field burst it might respond. He tries it and the head of the cane transforms into the ophidian the Devidians used to create the gateway. Tiny bursts of energy like bolts of lightning emanate from the snake which then transforms back into a cane. La Forge says they look like minute distortions in the space time continuum. Data remarks that the Devidians must have some device capable of concentrating the distortion. La Forge observes that anything that could focus them would produce high levels of triolic waves like in the cavern where Data's head was found. Data informs them that he has found that cavern.
An unexpected knock at the door and Mrs. Carmichael's voice intoning, "Mr. Pickerd!" interrupts them and everyone scatters to pre-arranged places. Troi answers the door as the others read from their Shakespeare playbooks. Picard tells Mrs. Carmichael that they need someone to read a part. He shows her where to read and she does so very stiltedly. Picard stops her and tells her how unique her reading was. "Really?" she asks. Mrs. Carmichael then tells Picard that she had done some acting in a play while in church when she was younger. Picard nods and announces that they have found their Titania. He tells her they start rehearsals tomorrow and kisses both her cheeks. She giggles.
Guinan is in Data's room waiting. Data returns and she announces that she has found a way to get into the mine shaft under the Presidio. Picard walks in behind Data. She stops speaking and stares. He returns her gaze and removes his hat. She asks if he knows her. He replies, "Very well." She then asks, "Do I know you?" Picard answers, "Not yet, but you will."
Outside the Sisters of Hope Infirmary, the reporter is finishing a conversation with the police officer who was struck by Riker. The police officer reminds the reporter to include the fact that he was the one who spotted Riker impersonating an officer of the law. The reporter turns and walks alone down the street and meets Clemens who says hello. He tells the reporter that he heard two people vanished into thin air in the infirmary. The reporter tells him yes, and that he was told a band of outlaws set off an explosion in the hospital and then escaped. Clemens asks what they looked like and learns that the carriage they escaped in was driven by an albino. Clemens exclaims, "They've come from the future. My God! It's an invasion!" and he quickly hails a passing carriage. The reporter asks him if he has any proof. Clemens promises to meet him at 4:30 with a story that will make his career. He gets into the carriage and says, "Take me to the Presidio, driver, and don't spare the whip!"
In the cavern under the Presidio, Riker notes that there triolic waves are just as high as those on Devidia II, but that he doesn't see any control mechanism. La Forge observes crystalline fractures in the rock wall with his VISOR. He says the entire cavern has been configured to focus the space time distortions like a lens, but he doesn't know if it will work with phaser power. Picard says they have to try.
"An event I most certainly would enjoy witnessing." says Clemens as he descends the stairs into the cavern. He holds a cigar in one hand and a revolver in the other. He then says he plans to take them all to the authorities. Data tells him it is imperative that they finish their mission. Clemens tells him to move and suspects that "even time travelers are vulnerable to the Colt .45. Let's go," he says, glancing at his pocket watch, "I don't want to be late."
Suddenly, next to Troi, the Devidians appear and snatch away the cane. Data grabs the cane and knocks the male to the ground. The cane emits many sparks and flashes before exploding. Everyone in the cavern is knocked from their feet and Data's head tumbles into the dirt, sparks dancing around his lifeless eyes. Picard sits up and sees the portal back to Devidia II open. The male Devidian checks his female companion and runs through the opening. He is followed by Riker, La Forge, Troi, and Crusher. Just as the portal begins to collapse, Clemens dives through, leaving Picard and Guinan alone in the cavern.
=== Act Four ===
Back on Devidia II in the 24th century, Riker is surprised to find Clemens is with them. Clemens asks, "Where are we? And when?" Riker explains, and adds that he's not supposed to be there. Clemens claims he has the same right to be in their time as they had to be in his. Riker tells him that the disappearance of such a prominent writer would be problematic to history. Lieutenant Worf's voice over the communicator interrupts them and Riker tells him to stand by to transport five. La Forge calls Riker's attention to Data's headless body lying on the cavern floor still clutching the cane. Riker tells Worf to transport six and they beam up to the Enterprise.
In the transporter room of the , Riker calls for security to escort Clemens just as Worf arrives. Clemens is startled when he first sees him and exclaims, "a werewolf." La Forge tells Crusher to have Data's body taken to the science lab where he'll try to reattach the head they have. Crusher reminds La Forge that that head is five hundred years old. La Forge responds that he knows but it is the best chance they have. Troi offers to escort Clemens to his quarters. They walk out together as Clemens asks if they've ever run into Halley's Comet.
In the San Francisco cavern, Guinan awakens in Picard's arms. She asks him why he stayed behind and he tells her that he had to make sure she was all right. He adds that she is far too important to him to let anything happen to her. Picard explains that in the future, their relationship will go far beyond mere friendship. Guinan laments that she'll have to wait 500 years and that she won't be able to tell him about it when they eventually meet for the "first" time. She notices Data's head and Picard comments that it is history fulfilling itself.
In Ten Forward, Riker is angrily pushing Guinan for answers to how to get Picard back. She refuses to tell him what had happened five hundred years ago in the cavern for fear it would change history and affect Riker's decision. Riker leaves in frustration.
Troi has changed into her regular uniform and is walking the corridors with Clemens who is craving a hand-rolled Havana cigar. He says that he's not impressed with the future with all its technology and the loss of simple pleasures like gentlemen opening doors for ladies. He speculates that they have terrible weapons on the ship and that military conquest is a way of life. He seems bemused at seeing a Bolian walk by them and reflexively assumes that his race has been enslaved by Humanity. They enter a turbolift and go to Deck 36. On the way, Troi explains that they live in a peaceful Federation and the Bolian isn't a captive, but rather one of the thousands of species they've encountered. Clemens supposes that they are privileged and that they probably ignore the poor. Troi tells him that poverty was eliminated on Earth a long time ago, along with many other ills of Human civilization. Clemens, caught somewhere between sarcasm and incredulity, says he comes from a time where inequality, prejudice, and the ruthless pursuit of power and wealth are the norm for Human behavior, "and you're telling me that isn't how it is anymore?" Smiling serenely, Troi responds yes. Clemens ponders her words and says that perhaps this future is worth giving up cigars for after all.
They exit the turbolift and enter the science lab where La Forge has reattached Data's head to his body. He explains that Data's activating units won't initialize. Clemens is pleased to find his watch on a nearby table and La Forge says that after five hundred years it probably won't work either. Clemens goes over to Data, taps his shoulder, and apologizes for misjudging him, as he has misjudged many things.
Back on Earth, the female Devidian awakens. Her arms and head sporadically flicker with blue light, revealing her true form. She asks Picard why they interfered with them. Picard says they are hunters and are killing Humans, they had to stop them. He tells her that the Enterprise is going to destroy their transport site on Devidia II. The Devidian tells him that they'll only amplify the time distortion and annihilate Earth. She flickers with blue light and disappears.
=== Act Five ===
In the observation lounge, Riker announces that he is going back for Picard. Worf says they should destroy the cavern immediately to stop the temporal incursions to Earth. Troi agrees and Riker concedes. He asks to be alerted when the photon torpedoes are ready.
In the science lab, La Forge is working with the computer to revive Data. The computer says the reload circuits are initializing, but La Forge still can't understand why he can't get Data to reactivate. He asks the computer to run a diagnostic on the input polarizers and finds there is only intermittent contact there. He goes over and opens a small panel on the back of Data's head and finds an iron filing in the circuitry. He wonders how it could have gotten there.
In the cavern on Earth in 1893, Picard goes over to Data's head and picks it up. He opens the back panel on his head and looks around the cavern. He finds an iron filing and begins to do something to the circuitry under the panel.
On the bridge, Worf informs Riker that the torpedoes are armed. Riker says to fire when ready. Worf replies that they will be ready to fire in only one minute.
La Forge, in the science lab, has the computer run another diagnostic on the input polarizers. They are now functioning properly and he activates Data's positronic brain and turns him on using the switch on his back. Data revives, turns to La Forge and says, "Torpedoes… Phasing… Alien…" He reaches back and adjusts something on the back of his head and tells La Forge he is processing a binary message entered into his static memory by Captain Picard. He then says it is imperative that they do not fire on the caverns. La Forge contacts Riker and tells him to hold his fire.
Later, on the bridge, Data is back in uniform and tells Dr. Crusher, Riker and La Forge that the message from Picard isn't entirely clear. He says Picard was concerned that the phase differential of the torpedoes might produce catastrophic effects. He says they need to modify the torpedoes so the force of the explosion is re-phased into the alien's time continuum. La Forge says he can fit the torpedoes with phase discriminators but it will take a couple hours. Riker decides he now has time to go back and get the captain. Crusher tells him that the phaser will probably work, but the rift will only be stable enough for one person. Clemens and Troi enter and overhear Crusher. Clemens says he should be the one to go, so he and Picard can return to their proper places in time. Clemens adds that he has more books to write, anyway. Riker agrees and orders La Forge to brief Clemens on what he needs to know. Clemens shakes Data's hand warmly and thanks him for starting him off on "the greatest adventure a man's ever had!"
Guinan, in the Earth cavern, tells Picard she is thirsty. He says he'll go for help when Clemens enters, with the cane in hand. He explains that, "This thing put me down in the middle of Market Street. It took forever to get here."
On the bridge, Worf tells Riker that the reconfigured torpedoes are ready. Riker says they'll wait five more minutes, then fire.
In the cavern, Clemens explains to Picard that La Forge got his message and that a frequency setting of .047 on the phaser will activate the ophidian. Picard asks Clemens to get help for Guinan and to settle the bill at Mrs. Carmichael's boarding house. He agrees to take care of both matters. Picard thanks Clemens, and explains that he wishes he could have gotten to know him better. Clemens points out that his personality is written in his books. Picard goes to Guinan and she says, "I'll see you in 500 years, Picard." He replies, "And I'll see you… in a few minutes." They part.
Data reports to Riker that he is picking up massive triolic wave activity on the surface, but there are no Human life signs or temporal distortions. Riker orders Worf to fire torpedoes. Just as the torpedoes are away, Data detects Human life signs on the planet.
In the Devidian cavern, Picard sits up and witnesses the Devidians flashing into and out of view just as Chief O'Brien beams him out.
Worf reports to Riker that the target has been destroyed. Riker orders the ensign to lay in a course for the nearest starbase at warp 6.
Picard enters Ten Forward to see Guinan. They both look upon each other with warmth.
:"Captain's log, Stardate 46001.3. Everyone who should be in the 19th century is safely there and those who should be in the 24th are here. Mr. Data has been restored to us, head and all, and Samuel Clemens will write the books he was to have written after our encounter."
In the Earth cavern, Guinan is carried away on a stretcher and Clemens assures her she'll be fine. He stops and picks up his watch and goes to put it in his pocket, then he remembers. He places the watch on the floor of the cavern not far from Data's head and leaves the cavern. Both the watch and the head wait on the cavern's floor for history to repeat itself…
== Memorable quotes ==
"I just want you to know that I have the utmost respect for the law." 
(Riker jabs a police officer in the face, knocking him down.)
:- Riker, to a police officer
"Young man, I have a maxim that I have always lived by: no one is more qualified to write your story than you are."
:- Samuel Clemens, to a young Jack London
"Shame on you, Mr. Clemens! Shame!"
:- Guinan, after she and Data discover Samuel Clemens hiding in a closet listening in on them
"A werewolf!"
:- Samuel Clemens, on seeing Worf
"Do you know me?"
"Very well."
"Do I know you?"
"Not yet, but you will."
:- Guinan and Picard, meeting for the "first" time in 1893
"I suspect that even time travelers are vulnerable to the Colt .45."
:- Samuel Clemens
"Where are we… and when?"
"This is the 24th century, we're on Devidia II and you're not supposed to be here."
:- Samuel Clemens, being briefed by Riker on his current location and time period
"The disappearance of Mark Twain, one of the most noted literary writers of the 19th century…"
"Thank you!"
"That's not supposed to happen."
"I only took advantage of an irresistible opportunity, as any good writer would."
:- Riker and Samuel Clemens
"You know an awful lot about me."
"Believe me, in the future, the tables will be turned."
:- Guinan and Picard, alone together in the cavern in 1893
"Young lady, I come from a time when men achieve power and wealth by standing on the backs of the poor, where prejudice and intolerance are commonplace and power is an end unto itself, and you're telling me that isn't how it is anymore?!" 
"That's right." 
"Hmm… maybe… it's worth giving up cigars for after all."
:- Samuel Clemens and Troi
"What's that?"
"That's history fulfilling itself."
:- Guinan and Picard, seeing Data's severed head in the cavern
"I'll see you in five hundred years, Picard."
"And I'll see you… in a few minutes."
:- Guinan, before Picard returns to the 24th century
== Background information ==
=== Production history ===
* Final draft script: 
* Premiere airdate: 21 September 1992
* First UK airdate: 
=== Story and script ===
* The staff found breaking the story very difficult. As with previous two-part episodes, the first installment had been developed without any consideration of how to conclude the story. Jeri Taylor recalled, "This one was a nightmare. It was just awful to try to get the story going. Even when we finally went to script, we kept changing the story so it was a matter of going back and wrenching out sections and restructuring and plugging in other things and then taking all that away again. It was probably the most troubled episode of the year." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 257)
* René Echevarria remembered, "We basically boxed ourselves into a corner with 'Part One' and it prompted very hilarious arguments about time travel and how it worked, 'That's not how time travel works, you idiot', with huge accusations and people falling back on primary sources like . 'That's the way it works, you can go meet yourself!' and all sorts of preposterous stuff." (Captains' Logs: The Unauthorized Complete Trek Voyages, pp. 256-257)
* When writing the teleplay, Taylor was inspired by the historical fiction of . ()
* Taylor sought to reduce the amount of technobabble compared to the first half. "We wanted to stay away from that. I think that in a sense, we might have gone too far, because I'm not sure that a lot of it was ever explained. I think it might still be mystifying to people – just what were those aliens up to and why were they doing it? Every time we started to get into all of this long stuff again, we decided we'd just go with the fun." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 256)
* An idea dropped due to time and budget would have had the crew staying in the past for several months. They would meet at a cafe run by Picard, where the running joke was how bad his food was. ()
* In the final draft script, Guinan claimed to be from a well-known Boston family and that she was a close relative of Judge Truman Williams. Clemens checked her story and received a telegram from Williams, who had never heard of Guinan. 
* In this episode, Samuel Clemens (aka Mark Twain) mentions that he wrote a book about time travel. He is referring to , which was published in 1889, four years before the episode's time setting. This book inspired the 1998 movie , starring Whoopi Goldberg. This book is also referenced in the episode , in which Kathryn Janeway gives a copy of said book to the holodeck character of Michael Sullivan.
* Towards the end of the episode, Captain Picard mentions, "Samuel Clemens will write the books he was to have written after our encounter." Indeed, Clemens wrote seven books after 1893; the last one () was published posthumously.
=== Production ===
* Unlike Part I, the scenes in the past were not shot on location. Originally, the producers had intended to film in a section of Universal Studio's back lot. However, over the show's hiatus, Paramount had rebuilt their New York Street set, and asked for it to be used instead. (Star Trek: The Next Generation 365, p. 268; Captains' Logs: The Unauthorized Complete Trek Voyages, p. 257)
* Various in-jokes were included in the set, such as "James Bank", "Okuda's Growing Seed". ()
* According to Production Designer Richard James, a museum loaned out a horse-driven fire vehicle for the first time thanks to "the power of the words Star Trek." ()
* The new "morphing" effect seen as the snake-head cane transforms was created to clarify the effect seen in . ()
* "Time's Arrow, Part II" was filmed at the same time as the pilot episode .
* As with many appearances where Dr. Crusher appears in flashbacks or other time period costumes, Gates McFadden's real hair was used in all the scenes where she wears her nurse costume. Her longer hair was curled and pinned. 
=== Cast and characters ===
* Alexander Enberg (the reporter), who is the son of Jeri Taylor, later played Taurik in and the recurring character of Vorik on for several years.
* While Whoopi Goldberg was usually only available for filming for a limited amount of time, she agreed to take on an expanded role here as she enjoyed the concept. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 249)
* Pamela Kosh (Carmichael) later played Jessel in .
=== Continuity ===
* In , Guinan tells Geordi La Forge she is attracted to bald men, because, long ago, one was very kind to her. In , Guinan tells Ro Laren that an old man helped her (Guinan) out when she was in serious trouble. Both references are seen here, when Picard saves her life in the 19th century.
=== Reception ===
* Michael Piller was pleased with the conclusion to the two-parter. "Any time you deal with time you're going to have complexities that are hard to grasp. But if you really look at that closely I think we got them all nicely stitched." ()
* Marina Sirtis enjoyed the period setting and costumes. She remarked, "It was fun […] It was nice to use the corsets, things that we were so uncomfortable in, since I would imagine someone coming back in time from the 24th century would be. It's always playtime when we have to do these things." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 257)
* Ronald D. Moore regretted that more wasn't done with the 1890s period. () He also felt that Mark Twain's involvement was too perfunctory. "To take that sort of historical figure and put him on the starship for an episode felt like there should be more than just one walk through the corridor with Troi. Unfortunately, there was so much story to tell that the needs of the show forced you into really moving that into a sidebar and just playing a scene here and there." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 256)
=== Awards ===
* This episode won two Emmy Awards. Only four other episodes of Star Trek have won this many. It won for Outstanding Individual Achievement in Costume Design for a Series (Robert Blackman) and Outstanding Individual Achievement in Hairstyling for a Series. It was also nominated for Outstanding Individual Achievement in Sound Editing for a Series.
=== Video and DVD releases ===
* Original UK VHS release (two-episode tapes, CIC Video): Volume 64, 
* In feature-length form, as part of the UK VHS release Star Trek: The Next Generation - The Full Length TV Movies: Volume 5, catalog number VHR 4105, 
* As part of the TNG Season 6 DVD collection
* In feature-length form, as part of the Star Trek: The Next Generation - The Complete TV Movies collection
* As part of the Star Trek: Fan Collective - Time Travel 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 ===
* Jerry Hardin as Samuel Clemens
* Pamela Kosh as Mrs. Carmichael
* William Boyett as policeman
* Michael Aron as Jack London
* James Gleason as Apollinaire
* Mary Stein as Devidian woman
* Alexander Enberg as young reporter
;And
=== Special guest star ===
* Whoopi Goldberg as Guinan
=== Co-stars ===
* Bill Cho Lee as Male Patient
* Majel Barrett as Computer Voice
=== Uncredited co-stars ===
* Majel Barrett as Narrator
* Teda Bracci as dead body
* Debbie David as Russell
* Tracee Lee Cocco as Jae
* John Copage as sciences officer
* Van Epperson as morgue attendant (deleted scene)
* Keith Gearhart as sciences officer
* Malachy Fergus Godfrey as San Francisco citizen
* John Hanna as buggy driver
* Bob Harks as priest
* Christie Haydon as command ensign
* Gary Hunter as sciences officer
* Leonard Jones as Bolian man
* Arvo Katajisto as Devidian man
* Brandy Pickett as civilian
* Keith Rayve as command ensign
* Robert Seeley as Devidian
* Victor Sein as command officer
* Talbot as Ten Forward waitress
* K. Uchizono as civilian
* Guy Vardaman as Darien Wallace
* Dru Wagner as 
* Christina Wegler Miles as command ensign
* Unknown performers as
** Eighteen San Francisco citizens
** Five patients
** Mercier's barrier carrier
** Sisters of Hope Infirmary doctor, nurse, and orderly
** Three policemen
** Two dead bodies
** Two Devidians
=== Stunt doubles ===
* Chris Doyle as stunt double for Arvo Katajisto
* Joy Hooper as stunt double for Whoopi Goldberg
* Tom Morga as stunt double for Jerry Hardin
* John Nowak as stunt double for Patrick Stewart
* Unknown stunt performers as
** Stunt double for William Boyett
** Stunt double for Brent Spiner
=== Stand-ins ===
* David Keith Anderson – stand-in for LeVar Burton
* Debbie David – stand-in for Brent Spiner
* Candace Crump – stand-in for Whoopi Goldberg
* Michael Echols – stand-in for Michael Dorn
* Nora Leonhardt – stand-in for Marina Sirtis
* Lorine Mendell – stand-in for Gates McFadden
* Richard Sarstedt – stand-in for Jonathan Frakes
* Dennis Tracy – stand-in for Patrick Stewart
=== References ===
19th century; 1850s; 1862; 1865; 24th century; ability; accomplice; alarm system; Alaska; albino; algid stage; army base; assayer; aurora borealis; brain stem; burner; cane; career; cerebellum; cerebral cortex; Chinatown; cholera; Christianity; cigar; city ordinance; Colt .45; confiscation; ; County Assayer's Office; coroner; Croquet Scene; cyanotic; Devidia II; Devidian; dozen; durum; Dutch; Earth; earthquake; E.B. Warehouse; egg cream; fairy; Federation; French; Frenchman; gadget; gas lamp; geological engineer; Geological Society; Halley's Comet; Hall of Records; ; hotel; Hotel Brian; hot fudge sundae; ice cream; investor; James Bank; Jesus Christ; Klondike; letter of intent; life story; London; marble; Market Street; Mary; maxim; ; Milan; ; neural depletion; neural energy; mineral shop; mining; ; nurse's cap; Oberon; Okuda's Growing Seed; ophidian; outlaw; Paris; phase differential; phase discriminator; Pickerd; ; Pops Candy Store; Portuguese; prejudice; Presidio; Puck; R.D. James Plumbing; R. Moore Grocery; rehearsal; root beer; San Francisco; San Francisco Police Department; San Francisco Register; seltzer; sequel; ; Sisters of Hope Infirmary; Spanish; station; surveyor; Swiss; Switzerland; tea dance; Titania; triolic wave; time traveler; tricorder; troupe; turbolift; unnamed starbase; vessel of exploration; waterfront; ward; werewolf; ; whip
==== Unused production materials ====
Ashanti; Boston; 
=== External links ===
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de:Gefahr aus dem 19. Jahrhundert, Teil II
es:Time's Arrow, Part II
fr:Time's Arrow, Part II (épisode)
ja:タイム・スリップ・エイリアン・後編（エピソード）
nl:Time's Arrow, Deel II
pl:Time's Arrow, część II