Similitude (episode)
During an engine performance test, Trip Tucker is critically injured and left comatose in sickbay. Phlox suggests that Tucker's only hope for survival is the creation of a "mimetic simbiot" – in other words, a clone. The crew and Trip's clone have to face the unforeseen emotional ramifications of his creation.

Summary

Teaser
At a funeral ceremony, the entire crew gathers as Captain Jonathan Archer is eulogizing a dead crewman – Commander Charles Tucker III.

Act One
Two weeks earlier, the  is continuing to explore the Delphic Expanse, and testing upgrades to their warp drive in order to do it more quickly. T'Pol and Tucker have another Vulcan neuro-pressure session and discuss it. This time, Tucker tries it out on T'Pol's foot, mostly successfully. The next day, they start the test. First, they get to warp 4.9 like normal, then Tucker starts to compress the antimatter stream in the warp core. It appears to work initially, but, unfortunately, only seconds later, a primary injector flare forces Tucker to do a manual shutdown. While on the top of the warp core, he is injured by a nearby explosion and falls. Helm control is lost and the Enterprise is thrown out of warp into a polaric field of some type. Emergency teams are dispatched to tend to multiple injuries, including Tucker's. 

Archer learns later that nucleonic particles flooded the plasma manifolds, causing the injector flare. Tucker's action saved the ship from a breach. It will be weeks before they can get the ship back to normal. T'Pol is in charge of repairs, and later has EV teams retrieve a sample of the particles from the field. The highly magnetic properties of the particles don't appear to be a problem now, but are building on the ship's hull and could become a problem if they are not able to clear the field in time. Archer tells T'Pol to do whatever it takes. 

Unfortunately, Doctor Phlox must inform Captain Archer that Tucker has slipped into a coma due to extensive neural damage. He has an unconventional proposal to use a Lyssarian Desert Larvae he happens to have to make a clone of Commander Tucker (which will grow to maturity very rapidly, and have a lifespan of only about fifteen days) and harvest neural tissues from it. Because of highly sensitive ethical implications, Archer does not make a decision right away. Soon, however, Archer agrees to allow the cloning procedure, sacrificing the ethical implications for the sake of the mission's objective, and perhaps the life of his friend.

Phlox informs Archer the procedure was a success, and Archer sees the new infant.

Act Two
Phlox, pleased at holding a newborn after a long time, informs Archer and T'Pol the infant is healthy, though needs a name. He calls him Sim. The clone quickly grows from an infant to a child. Sim can read soon, though interestingly, the boy demonstrates that he has the memories of Tucker at the same age, including his family, by saying he already knows what the book is about. Sim is as curious about the world as Tucker is, both about technology and about his existence. Archer decides to be the one to tell him the truth, and takes him to his quarters and they have small talk, with Sim pointing out Zefram Cochrane on the wall. They then go to the launch bay to fly a remote-controlled model, and the real questions start. Archer takes Sim to sickbay, where Tucker's body is. Sim recognizes Tucker and gets it all on his own. Archer does say Sim's more than just a copy, since he's making his own memories. He also says Tucker needs something from him, and that the operation is painless. Sim believes them and wants to go fix the model, seemingly taking it all very well. 

As Sim ages, he starts to help with the repairs. He's happy to do it, though disappointed when he thinks T'Pol doesn't want to hang out with him because he's different. T'Pol insists they need to be focused on the repairs. She's called away by Archer to find that the particles building on the hull have a dampening field effect, and that at the rate the crew has been proceeding, every system on the ship will fail before the repairs are complete.

Act Three
Sim soon comes up with a solution to the ship's problem, and, while trying some key lime pie, he runs it by Malcolm Reed in the mess hall. Reed confirms they could re-direct the phase cannons to fire at the launch bay so they can launch the s. Sim also runs the idea by T'Pol later that night and, although risky, she agrees it appears to be the only viable option. It involves a fusion overburn, which has never been attempted by a shuttlepod. Sim turns the conversation to her and Tucker's relationship, confesses his feelings for her, and wondering if they're his or Tucker's.

Later, Sim goes to Archer and insists he pilot one of the pods since it is his plan, but the Captain assigns Reed and Travis Mayweather instead. Sim challenges his decision on the basis that he's only concerned about Tucker, but Archer points out (again) that they need Tucker to survive. 

The plan begins. Sim and T'Pol set the targeting scanners of the cannons and fire, successfully freeing the launch bay. Reed and Mayweather fly out and fire their respective grappling arms. Sim orders their thrust power and they try to pull the Enterprise, but it's not moving. They push their engines a little harder and, just as Archer decides to abort, the ship starts moving. The plan is a success, as their inertia will keep them going, and they'll be out of the field in six hours.

Later, Phlox informs the captain of a startling discovery. According to his new predictions, and contrary to his earlier determination, Sim won't survive the transplant because Human DNA is not as resilient. Archer's decision just got a lot more difficult.

Act Four
Sim is devastated to hear this news, though he does say he only has a few days left, anyway. Archer doesn't see it that way, but then Sim states another complication: experiments by the Velandran Circle on mimetic simbiots claimed to have created an enzyme which could slow Sim's rapid aging and let him live a normal lifespan. Phlox didn't mention it because the enzyme was experimental and there's almost no actual evidence that it works. Also, in the time it would take to create the enzyme Sim's neural tissue would no longer be compatible will Trip. Despite that, Sim is insistent that there's a chance he can live a normal life. 

The next day, Archer finds Sim in Tucker's quarters, obviously dwelling on Tucker's life. He begins to question why his life is not seen to be as valuable as Trip's. He confronts Archer about the situation, saying he didn't control what happened to Trip, and he, in a way, could be saving him by taking on his life. Archer is insistent that Sim is not Trip, and that he will stop at nothing to complete the mission, which requires Trip. He appeals to the fact that Sim has Tucker's memories, so he knows Archer's resolve. Sim doesn't think Archer will murder, but Archer tells him not to make him a murderer. 

Sim later has agreed to the procedure, and goes to engineering to help out T'Pol beforehand. She wonders why he wants to spend his last hours of life like that, but gives him something to do. Later, Reed finds out on the bridge that launch bay controls have been tampered with. Archer goes down there to find Sim having planned but then aborted an escape attempt. Sim says that what stopped him was the thought of his sister, insisting on the fact that she was his sister as well as Trip's, and that he doesn't want what happened to her to happen to anyone else. He leaves to go back to his quarters to wait. Just before the surgery, T'Pol comes to Sim's quarters to say her goodbyes, giving him a kiss, something she had never done with Tucker. Sim returned the gesture, showing that he meant something to her, more than just being a clone to save Trip's life.

Sim goes to Sick Bay, where Phlox and Archer are waiting. Sim tells Phlox he doesn't just remember Trip's childhood, he remembers his own, and Phlox was a "damn good father." Phlox says Sim was a damn good son. Sim then tells Archer that just as Archer was meant to be a starship captain, he realizes saving Trip's life is what he was meant to do. In his final preparations, he stands near the comatose Trip and says, "You owe me one."

Back in the present, at the funeral ceremony, the crew, including a recovered Trip, pay their last respects to Sim as he is placed in a torpedo tube and fired out into space.

Memorable quotes 
"The most difficult test facing any captain, any crew, is the loss of a shipmate. We've come here to honor one of our own. In the time we knew him, he showed us just how much one life can truly matter. We will never forget what he did for us, and for the ship he loved so much. We will go forward with renewed determination to complete this mission, so that his sacrifice won't just have been for the people on this ship, but for all the citizens of Earth."
 - Captain Archers eulogy for a lost crewman, apparently Trip Tucker

"Regarding the Lyssarian procedure Doctor Phlox proposed, may I ask if you've reached a decision?"
"I approved it."
"Are you aware that the Lyssarian Prime Conclave has banned the creation of simbiots?"
"We don't answer to the Lyssarian Prime Conclave."
"Simbiots are living, conscious entities. We'll be growing a sentient being for the sole purpose of harvesting tissue."
"I'm aware of the ethical implications. If we weren't in the Expanse, maybe my decision would be different. But… we've got to complete this mission. Earth needs Enterprise. Enterprise needs Trip. It's as simple as that."
 - T'Pol and Captain Archer, discussing the controversial procedure Phlox has proposed in order to revive Tucker

"Can he do any tricks?"
"I haven't taught him any. Mostly what he does is eat, sleep, and, uh, not fetch."
 - Young Sim and Archer, discussing Porthos

"I'm not talking about an adolescent crush. That was… well, that was two days ago."
 - Sim, to T'Pol

"I have his memories. I have his feelings. I have his body. How am I not Trip?"
 - Sim, to Archer

"I must complete this mission! And to do that I need Trip! Trip! I'll take whatever steps necessary to save him."
"Even if it means killing me?"
"Even if it means killing you."
 - Archer and Sim, arguing over his right to survive

"I was all ready to do it."
"What stopped you?"
"Where the hell was I going to go? We're nowhere near any habitable planet. Didn't really want to spend the rest of my life floating around in a shuttlepod, which doesn't even have any toilet facilities. Can you imagine a lousier way to spend your old age – cooped up in that thing, peeing in a bottle? Actually, I can imagine a worse fate."
"What would that be?"
"Being stuck in there with Malcolm!"
 - Sim and Archer, with an obvious reference to Tucker's experience as documented in the season one episode, 

"It's not that I'm scared of dying. It's just that… I can't imagine not being here tomorrow."
 - Sim, to Archer

"Do me a favor when this is over. If Commander Tucker decides to do any more modifications to the engines… tell him to watch his ass!"
 - Sim, to Archer

"I'm sorry I doubted you, Doc."
"No need to apologize."
"Yes, there is. You see, I don't just remember Trip's childhood. I remember mine. You made a damned good father."
"You were a damned good son."
 - Sim and Phlox

"You said to me once that commanding a starship was what you were meant to do. I guess this is what I was meant to do. Good luck, Captain."
 - Sims last words to Archer

"You owe me one!"
 - Sims last words, to the still comatose Tucker

Background information

 This episode marks the first written contribution of then-new Co-Executive Producer Manny Coto.
 The final draft script of this episode was archived on .
 In the final draft script of this installment, Archer replied to Sim hoping that his sister's fate doesn't happen to anyone else by commenting, "That's why we're out here." In the final version of the episode, though, Archer instead says, "That's why I gave the order to create you."
 Adam Taylor Gordon, who played a younger version of Tucker in , played the version of Sim at age 8 in this episode.
 John Billingsley named "Similitude" as one of the strongest episodes of the third season. 
 The model Archer played with as a boy in  reappears in this episode.
 This is the first occurrence in the Star Trek universe, chronologically, of a funeral on board a starship.
 This is also the first chronological mention of a tricorder (in reference to Phlox' medical tricorder) and the only occurrence of that word in the series.
 Pondering his final moments in a , Sim mentions sharing his agonies with Malcolm Reed which is a reference to Trip's memories from , where he was trapped with Reed in a pod.
 This episode establishes that NX type shuttlepods do not have any bathroom facilities.
 Chronologically, this is the first time we witness a photonic torpedo casing being used as a coffin for the deceased in Starfleet funeral proceedings. The practice is essentially repeated, though with a photon torpedo instead, in .
 In a rare break with continuity, when the shuttlepods are attempting to tow Enterprise out of the particle field, Lieutenant Reed uses kilodynes to measure the amount of force that is being applied. Dynes are part of the legacy centimetre-gram-second system of units (CGS). Except for , where old imperial units such as miles are sometimes used, Star Trek episodes and motion pictures normally apply the International System of Units where force is measured in newtons. It is worth noting that dynes were named by Joseph David Everett, an Englishman, as is Reed.
 Brannon Braga was delighted with this episode. "Manny just knocked it out of the park," Braga remarked. "He wrote a great script. Connor Trinneer gave a terrific performance. And you know the arc is working because 'Similitude' just wouldn't have worked last year. You needed the context of the Xindi arc to give it its power, to give Archer those tough decisions. Additionally, T'Pol learns that Trip's in love with her, but the real Trip doesn't know that she knows! That set up great dynamics for upcoming episodes." ()
 This episode won an Emmy Award for Velton Ray Bunch's music composition.
 This outing was popular with fans due to its moral complexity. () The episode was chosen as the #3 fan favorite in an online poll conducted by UPN. It was re-broadcast on  in that context. Note: The poll was conducted before the final six episodes of the series had aired.
 The book Star Trek 101 (p. 260), by Terry J. Erdmann and Paula M. Block, lists this episode as one of the "Ten Essential Episodes" from Star Trek: Enterprise.
 Interestingly, the shuttlepods would have had no difficulty pulling or pushing Enterprise out of the nebula, as there is no gravity in space when the ship is far enough from any stellar bodies, as seems to be the case here. Inertia would cause Enterprise to retain any momentum imparted by the pods, even incrementally.

Links and references

Co-Stars 
 Adam Taylor Gordon as Sim-Trip at 8
 Shane Sweet as Sim-Trip at 17
 Maximillian Orion Kesmodel as Sim-Trip at 4

Uncredited Co-Stars 
 Adam Taylor Gordon as Young Trip (photograph)
 Breezy or Windy as Porthos
 Connor Trineer as Sim-Trip (adult)
 Unknown performers
 Sim-Trip's funeral attendees
 Baby Sim-Trip
 Elizabeth Tucker (young; photograph)

References
A Night at the Opera; acceleration; antimatter injector; aptitude; ; architecture; armadillo; Bedford; birthmark; bruise; cannula; cerebrum; ; coma; clone; cut; Delphic Expanse; Dennis; Denobulan; diagnostic; diamagnetic field; diaper; DNA; dollhouse; Earth; empirical evidence; engineer; Enriquez; epidermal layer; ethical implications; EV team; feces; ferric ion; fertilizer; field coil; funeral; fusion overburn; garden snake; genetic memory; genetic sequencing; glue; growth cycle; high warp; horse; injector flare; injector port; key lime pie; kilodyne; kilometer per hour; launch bay doors; life cycle; Lyssarian; Lyssarian Desert Larvae; Lyssarian Prime Conclave; magnetism; Martian; Marx Brothers; Massaro; medical tricorder; mimetic simbiot; name; neural nodes; neural tissue; nucleonic particle; Orsic fern; phase cannon; physical age; plasma assembly; plasma rifle; playing cards; REM cycle; roommate; salve; ; Shuttlepod 2; species; Steven; system tap; targeting scanners; temperature; toilet facility; teething stage; ; ; urination; Velandran Circle; viral suppressant; Vulcan; Vulcan neuro-pressure; ; warp drive; Xindi weapon; Zefram Cochrane's statue

Deleted references
fetching; ocean skimmer; statistics; suspensor coil

External links 
 
 
 

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