(written from a Production point of view)
A specially-outfitted warp-capable shuttlecraft piloted by Tom Paris successfully reaches Warp 10, breaking the transwarp barrier. But the side effects of breaking the barrier may cost the crew of Voyager their best helmsman.
Tom Paris is in an experimental shuttlecraft, attempting to break the warp 10 barrier. He brings the Class 2 shuttle up to warp 9.95, when the nacelles are suddenly ripped from the shuttle and it seemingly explodes. Paris appears, sitting on the holodeck floor, as if nothing happened; it was all a holographic simulation. Harry Kim looks despondent, and B'Elanna Torres responds matter-of-factly, "You're dead."
The trio go to the mess hall to consider how to fix the problem. Neelix offers to help, but they don't believe he can contribute anything to the discussion. Paris inquires if he knows anything concerning quantum warp theory and multispectral subspace engine design. Insulted, Neelix informs them that serving for two years as an engineer's assistant aboard a Trabalian freighter makes him well versed in warp theory and demands to know what they're up to. They finally fill him in: after months of experiments, Paris, Torres and Kim believe they have found a way to cross the transwarp threshold using a new form of dilithium they discovered in a survey of an asteroid field that remains stable at higher warp frequencies. Achieving warp 10 would allow a person to be in every point in the universe, simultaneously. Kim notes that getting home could be as quick as the push of a button. A problem occurs when the ship reaches warp 9.95, when microfractures appear and tear the nacelles from the ship. Neelix recalls an anecdote from his past when his ship was traveling through a dark matter nebula. Kim is initially dismissive, as this is a totally different phenomenon, but Paris realizes that it is actually the shuttle being ripped from the nacelles, not the other way around. While Kim confirms the tritanium alloy hull could depolarize at that speed, Paris continues, saying that could create a velocity differential, the fuselage traveling faster than the nacelles. As Kim infers, they could fix the problem by installing a depolarization field around the fuselage. Paris refers to the confused Neelix as a genius and runs out to the holodeck with Torres and Kim.
In the briefing room, the senior staff watch the holodeck simulation on the computer monitor and grin as Paris successfully brings the shuttle to warp 10 and crosses the transwarp threshold. Captain Janeway gives Paris the opportunity to start a manned test flight in a real shuttlecraft. She says he has the opportunity to join such great names as Orville Wright, Neil Armstrong, and Zefram Cochrane. Everyone is excited because, if this works, then it would mean much more than just getting USS Voyager home; it could begin a whole new era of exploration for Starfleet.
Janeway enters Paris' quarters that night, with news that The Doctor discovered an enzymatic imbalance in his cerebellum that appeared during the holodeck simulation; the subspace stresses could kill him from a brain hemorrhage, although the chance is only two percent. Not wanting to risk this chance, Janeway plans to assign Ensign Kim to the flight. Paris begs her to reconsider, stating that people have always said he was going to do something special someday, and that this is it. Janeway agrees to it, and the next morning Paris boards the shuttlecraft, now named Cochrane, and launches it. The shuttle kicks into warp, followed closely by Voyager. After running a few scans on the Cochrane's warp field at warp 9.7, Torres clears Paris for transwarp. Voyager increases to warp 9.975, its maximum velocity, for as long as it can but, as Paris quickly surpasses that speed, Voyager must slow and switch to long-range sensors to track him. As the crew waits in anxiety, Paris goes faster and faster until, finally, sensors record warp 10. Then, the Cochrane vanishes.
A search fails to turn up the Cochrane, but then it reappears. Lieutenant Paris is still on board, but unconscious, with weak life signs. In sickbay, The Doctor scans him and observes that Paris is merely sleeping. The Doctor abruptly wakes Paris and he recounts his transwarp flight to Captain Janeway. He says he was staring at the velocity indicator (which read warp 10) and then, suddenly, he noticed he was watching himself. He could see the outside of the shuttle, Voyager, the inside of the ship, and the sickbay. For a moment, he was everywhere, with the Kazon, the Klingons, on Earth, and he even saw other galaxies. He says it wasn't like anything he has ever experienced. According to Paris, he only returned because he noticed that the crew was looking for him. Torres bursts into the room and says that the on-board shuttle sensors confirm he flew warp 10, making Paris the first Human to break the transwarp barrier. Paris asks Torres to download the shuttle's data core while The Doctor runs further tests on him.
Kim downloads the shuttle's data into the engineering computer core – over five billion gigaquads of information – including detailed information on "literally every cubic centimeter" of the sector. Janeway orders the data sent to stellar cartography for analysis and the creation of a star chart.
After being released from sickbay, Paris is in the mess hall with Torres, where they are planning another flight to replicate the results of his first test. He begins to say the shuttle's memory core should be increased when, all of a sudden, Paris feels ill. First, he has a sip of Neelix' new Paris Delight blend of coffee and says it's awful, though Torres says it smells all right. Then he experiences a stomach ache, and then collapses to the floor writhing in pain. Torres asks the transporter room to beam him to sickbay but they respond by saying that they can't lock onto him; his pattern keeps changing. Torres calls for medical assistance and tells Paris to hold on.
The Doctor examines Paris in sickbay and says he had an allergic reaction to, of all things, the water in Neelix's coffee. In fact, Paris' entire body is mutating and his lungs are no longer processing oxygen. The Doctor replaces the atmosphere in the surgical bay with 80% nitrogen and 20% acidichloride. Paris can now breathe but a bigger problem has also developed; he is suffering from cellular degradation and is consequently dying.
The Doctor and Kes begin using radiation to try to stop it, with little success. Paris becomes delirious, asking for a huge funeral, saying he doesn't trust anyone that doesn't cry (like Torres) and remembering his childhood, when he used to cry in his room. He tells The Doctor that he lost his virginity at seventeen, in his room, which The Doctor says he will note in Paris' medical file. Paris exclaims he wants a pizza with pepperoni and Kavarian olives. He wants a kiss from Kes but she can't grant him that wish, because of the atmosphere in the surgical bay. Before he dies, he makes a last request; to tell his father that he did it. He tries to form another sentence but falls unconscious. The Doctor uses a neural stimulator to attempt to revive him but fails. The Doctor announces Paris' time of death and plans to perform an autopsy in the morning. Kes kisses Paris' apparently lifeless body before she leaves sickbay.
That night, as The Doctor is working in his office, he hears a strange rattling in the other room. Uncovering Paris' body, he discovers him alive and well. Paris looks at his hand, then reaches up and pulls out a clump of his hair and demands to know what's happening to him. The Doctor scans him and finds something peculiar; Paris now has two hearts.
Crewman Michael Jonas, in his quarters, covertly sends data on the warp 10 shuttle flight to Rettik, his contact among the Kazon. Although Rettik doesn't believe it, Jonas sends him the entire file in an attempt to prove his worth to the Kazon-Nistrim.
The Doctor briefs Janeway on Paris' condition. He cautions her that not just Paris' body but also his personality is affected, he keeps switching from his original personality to one that seems deranged.
Janeway walks into sickbay to see a mutated Tom Paris lying on the biobed behind an isolation field. Paris says he feels "like a lab experiment that went wrong." She offers to help, but Paris' personality switches and he becomes furious. He says he is glad that he's changing and thinks that whatever he will become will be better than what he ever was. He demands that they stop trying to reverse his mutation. He doesn't believe anyone likes him and, in fact, he suspects they're jealous that he broke the warp 10 barrier. Janeway walks away and concedes there's nothing she can do. Paris' personality switches back again and he pleads with Janeway to help him, but then he lashes out, hitting the isolation field in front of him. He begins to tell Janeway how small and insignificant she is, when he starts to choke. Paris then vomits out his tongue and smiles.
Later, Kes discovers that Paris' rate of genetic mutation has accelerated by another 12 percent. The Doctor and Kes must hurry to save the last fragment of Paris' original Human DNA. Paris pleads to be let off the ship. They refuse.
After further analysis, The Doctor derives a treatment. He plans to revert Paris' body back to its original genetic coding by destroying the mutated DNA using anti-proton radiation from the warp core. They have to have the system set up in an hour if they hope to save him.
Paris has mutated even further. He is in a restraint situated next to the warp core in main engineering. The core shuts down to give Paris a two-second burst of anti-protons, but it's not working. Paris begins to struggle out of the restraints. The Doctor asks Torres to start a five-second burst of anti-proton radiation, when a commotion is heard in the background. Paris bursts out of his restraints. Phaser fire erupts in engineering, then the engineering screen where The Doctor was observing the procedure goes dark. The lights in the room start to flicker; Paris ruptured the port plasma conduit on his way out of engineering, causing power failures all over the ship. Tuvok announces a level 3 security alert over the comm system.
Janeway is on Deck 6 outside a turbolift when Paris attacks her from behind. She manages to fire her phaser, triggering the internal sensors, but they are malfunctioning due to the power failure. Consequently, the bridge can't localize her exact position. However, Kim is able to report that the captain is between sections 21 and 27 Alpha. Chakotay orders Tuvok's security personnel to that section of the ship, but it is too late. Paris takes Janeway to shuttlebay two and launches the Cochrane. The shuttlecraft immediately speeds to warp. Just then, main power on Voyager is restored and the ship heads after the Cochrane in pursuit. Voyager capably follows the shuttle until it reaches warp 9.975. Chakotay pushes the ship's acceleration even more, but slows back when the main computer issues a warning that Voyager's structural integrity will fail in 45 seconds. Paris and Janeway meanwhile cross the transwarp barrier, becoming no longer visible from Voyager.
- "First officer's log, stardate 49373.4. It's taken us three days to locate the shuttle. It appears to have dropped out of transwarp in an uninhabited star system."
After summoning Tuvok and Chakotay to sickbay, The Doctor observes that what happened to Lieutenant Paris was an accelerated form of natural Human evolution that would otherwise have taken millions of years. It is possible that Paris shows an advanced form of Human life. The Doctor comments that the lifeform isn't very attractive. He is still confident that the anti-proton radiation will work to revert Janeway and Paris back to their original Human DNA.
Kim reports, from the bridge, that ship's sensors have located the Cochrane on a remote planet in one of the jungles near the equator. Chakotay and Tuvok beam down with an away team to investigate. On the planet, they see two amphibian-like beings. Chakotay checks them with his tricorder and finds traces of Human DNA. The two have apparently reproduced, as there are several juveniles of the same species nearby. Chakotay stuns the two adult creatures with his phaser and brings them back on the ship. Chakotay has no idea which creature is Janeway. However, Tuvok notes the obvious deduction that Janeway must be the female.
- "First officer's log, supplemental. We've transported the captain and Mr. Paris back to sickbay. As for their… offspring, I've decided to leave them in their new habitat."
Paris and Janeway are reverted back to their Human selves using The Doctor's anti-proton treatments. Afterwards, Paris is extremely embarrassed about having mated with the captain, though he says he hardly remembers the whole event. Janeway accepts his apology, but admits that she might have also been active in the mating process; she may even have been the one who initiated it. Janeway puts Paris in for a commendation for his achievement. "Regardless of the outcome, you did make the first transwarp flight." Paris admits he has a few more barriers to break to build his self-esteem, but Janeway believes he will eventually overcome them.
"Can you wake him?"
"I don't see why not. WAKE UP, LIEUTENANT!'"
- - Captain Janeway and The Doctor, on Paris
"You're not going anywhere. At least not for a few hours. I have some tests I'd like to run on Your Majesty before I release you back into the realm of ordinary Humans."
"You may proceed."
- - The Doctor and Paris, after Paris returns from his mission
"My teachers at school, all the kids, everyone used to say 'Tom Paris is gonna do something important when he grows up.' Obviously, that didn't happen."
- - Tom Paris
"Do you have anything to eat?"
"Sure, there's some Kalavian biscuits somewhere in the kitchen."
"I guess I'll go get them myself."
- - B'Elanna Torres and Neelix
"In principle, if you were ever to reach warp 10, you'd be traveling at infinite velocity."
"Infinite velocity, got it. So, that means very fast."
- - Harry Kim and Neelix
"Maybe we've been looking in the wrong place. What if the nacelles aren't being torn from the ship; what if the ship is being torn from the nacelles?"
"The hull of the shuttle is made of tritanium alloy. At the speeds we're talking about, that alloy could depolarize…"
"And create a velocity differential! The fuselage would be traveling at a faster rate of speed than the nacelles!"
"That means we just have to set up a depolarization matrix around the fuselage!"
"That's it! Neelix, you're a genius!"
"I have no idea what they just said."
- - Tom Paris, Harry Kim, and Neelix, solving the problem of traveling at transwarp with technobabble
- - Kathryn Janeway and Tom Paris
"If Voyager achieved warp ten, we could be home in as long as it takes to push a button."
- - Harry Kim and Neelix
"Transwarp engines are stable, so are the nacelle pylons. I'm going to try to… Oh my God!"
- - Tom Paris, reporting in while at warp 10
"Commander, someone's opening the shuttlebay doors."
- - Harry Kim and Chakotay
"For a moment, I was everywhere. I mean, everywhere, captain. With the Kazon, back home with the Klingons, other galaxies, it was all there!"
- - Tom Paris, on his transwarp experience
"Ugh, I wish Neelix would name something after me that tasted a little better."
- - Tom Paris, after tasting Neelix's Paris Delight coffee
"What did he ingest?"
"Just a cup of Neelix's coffee."
"It's a miracle he's still alive."
- - The Doctor and B'Elanna Torres, after Paris first falls ill
"You are losing me, aren't you? I'm gonna die."
"You are too stubborn to die, Mr. Paris."
- - Tom Paris and The Doctor
"Pepperoni! God, I'd love a pepperoni pizza with Kavarian olives right now. I'm starving!"
- - Tom Paris, undergoing one of his evolutionary changes
"Here lies Thomas Eugene Paris, beloved mutant."
- - Tom Paris, aloud in sickbay
"Great! Now it will read '…beloved radioactive mutant!' "
- - Tom Paris to The Doctor, regarding a radiation treatment
"I lost my virginity in that room. Seventeen. Parents were away for the weekend."
"I'll note that in your medical file."
- - Tom Paris and The Doctor
"I don't know how I'm going to enter this into the log."
"I look forward to reading it."
- - Chakotay and Tuvok, after discovering Paris and Janeway's amphibious "children"
"I've thought about having children, but I must say I never considered having them with you."
- - Captain Janeway, to Tom Paris after The Doctor restores their Human DNA
"Not you, her."
- - Paris and The Doctor, the former referring to Kes
"I'm picking up traces of Human DNA… it's them. Although, I have to admit, I'm not sure which one is the captain."
"The female, obviously."
- - Chakotay and Tuvok, after discovering Paris and Janeway
"It's possible that Mr. Paris represents a future stage in Human development… although I can't say it's very attractive."
- - The Doctor
"The present and the past, they're both in the future!"
- - a mutated Tom Paris in sickbay
Story and script
- The story idea for this episode came from Michael De Luca, who was – at the time – the head of New Line Cinema. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages; )
- Tom Paris was used as this episode's central character because Star Trek: Voyager's writing staff believed he had become underused as the series' first season had progressed. (Cinefantastique, Vol. 28, No. 4/5, p. 91)
- The writers began developing the story by asking themselves what it might be like to break a fundamental rule of the Star Trek universe that had existed ever since the early days of Star Trek: The Next Generation. Jeri Taylor recalled, "Gene [Roddenberry] made the determination at the beginning of Next Gen that warp ten would be the limit, and at that point you would occupy all portions of the universe simultaneously, which always seemed like a wonderfully provocative notion. Then the question is 'What happens if you do go warp ten, how does that affect you?' So we all sat in a room and kicked it around and came up with this idea of evolution and thought that it would be far more interesting and less expected that instead of it being the large-brained, glowing person, it would be full circle, back to our origins in the water. Not saying that we have become less than we are, because those creatures may experience consciousness on such an advanced plane that we couldn't conceive of it. It just seemed like a more interesting image." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages)
- A working title of this episode was "Untitled Warp 10". 
- Supervising producer Brannon Braga later commented, "I wrote the episode, or at least the teleplay […] And… it had some good intentions behind it. It had a good premise, breaking the warp ten barrier. I don't know where this whole 'de-evolving into a lizard' thing came from […] I think I was trying to make a statement about evolution not necessarily being evolving toward higher organisms, that evolution may also be a de-evolution. You know, we kind of take it for granted that evolution means bigger brains, more technology, you know, more refined civilization. When in fact, for all we know, we're evolving back toward a more primordial state. Ultimately, who can predict?" (VOY Season 2 DVD easter egg) In a 2011 interview, Braga stated, "I was trying something [....] It was my homage, I guess, to David Cronenberg's The Fly." 
- Paris actor Robert Duncan McNeill was bewildered by the episode's first draft script. "When I read the first draft," he said, "I couldn't get it. I thought they took on much more than could be handled in one episode." (The Official Star Trek: Voyager Magazine issue 11) He also remarked, "When I first read that script, I couldn't believe they were going to shoot it." (Cinefantastique, Vol. 28, Vol. 4/5, p. 94)
- Robert Duncan McNeill helped refine the episode's conclusion. "I helped them rewrite the episode's final scene. I did not feel the original story ended very well. I was pleased because I got to have some input into how to resolve the story." (The Official Star Trek: Voyager Magazine issue 11)
- In fact, Brannon Braga thoroughly edited the script during the rewrite process. He remarked, "It's very much a classic Star Trek story, but in the rewrite process I took out the explanation, the idea behind the ending, that we evolve into these little lizards because maybe evolution is not always progressive. Maybe it's a cycle where we revert to something more rudimentary. That whole conversation was taken out for various reasons, and that was a disaster because without it the episode doesn't even have a point. I think it suffered greatly. I got the note that it wasn't necessary, but in fact it really had a lot to do with what the episode was about. Big mistake taking it out." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages) Later, Braga complained, "Unfortunately, none of [the evolutionary theorizing] came across in the episode. And all we were left with were some lizard… things crawling around in the mud. So, it was not my shining moment." (VOY Season 2 DVD "easter egg") In 2011, he named this episode as the one installment from the entirety of Voyager that he would "just as soon forget" and remarked, "That's a real low point […] It really backfired on me. It was poorly executed by me." 
- This episode's final script draft was submitted on 31 October 1995. 
- Regarding the hypothetical concept of infinite velocity, science consultant André Bormanis remarked, "It's fun to invoke paradox when you're talking about something as bizarre and as hypothetical as warp drive. And so, that idea become the basis for a story where Tom Paris thought that he had figured out a way to sort of 'crash' the warp 10 barrier and was eager to try to implement this, and see if he could actually achieve warp 10 flight […] Unfortunately, when Paris did achieve warp 10 flight, it had all sorts of unintended consequences and, physiologically, he started mutating and turning into something bizarre and strange. And the story went off in a really unconventional and kind of horror movie direction, after he had broken the warp 10 barrier. But all of that is basically the consequence of taking one of Gene's original ideas, from the beginning of Next Generation, and extrapolating and playing with it and finding an interesting way to use that as the springboard for a fun science fiction story that we can tell with our crew." (Real Science With Andre Bormanis, VOY Season 2 DVD special features)
- André Bormanis believed the first part of the episode, involving Paris breaking the warp 10 barrier, had similarities to a certain historical event. "It was a little bit of an analogue to breaking the sound barrier," Bormanis commented, "the famous story about Chuck Yeager and the X-1 in 1947, finally breaking the sound barrier." (Real Science With Andre Bormanis, VOY Season 2 DVD special features)
- In the shooting script of this episode, the eponymous shuttlecraft that breaks the warp 10 barrier is named the Drake. However, a shuttlecraft of that same name is destroyed in the earlier second season episode "Non Sequitur". The eventual name of the shuttlecraft here was the Cochrane, named after Zefram Cochrane. (Star Trek: Voyager Companion)
- Robert Duncan McNeill was generally puzzled by this episode, so he tried to rationalize it for himself. "When you try to tell the story–he breaks warp ten, starts shedding skin, he kidnaps the captain and then he becomes one with the universe, [he and Janeway] are salamanders, and have a baby–it sounds ridiculous," McNeill remarked. "What is this about? Before you can even start to tell the story you have to find the moral. What is the simplest point of this episode? Once you can say that in a sentence then that is what the episode is about. To me […] the whole warp ten [challenge] and salamanders and all of that frosting was about Paris trying to find some sort of salvation outside himself and ultimately realizing that he had to find his own self worth from within. Here is somebody who thinks he's got to break warp ten and prove to everybody, his father and himself that he can do this outside thing, but ultimately your happiness comes from within." (Cinefantastique, Vol. 28, Vol. 4/5, p. 94) In the end, McNeill still thought the episode was very strange. "That was a bizarre show," he exclaimed. "It really was." (The Official Star Trek: Voyager Magazine issue 11)
- On the other hand, Robert Duncan McNeill also enjoyed scenes that were important for his character, especially one that essentially epitomizes his interpretation of the plot. He enthused, "I like a few scenes that I thought were important for Paris. I like the one where I explain to Janeway how I need to prove myself by breaking the warp speed barrier." (The Official Star Trek: Voyager Magazine issue 11)
- Despite his mixed feelings about the story, Robert Duncan McNeill extremely liked appearing in this installment. He described it as "[an] episode I really enjoyed" and, moments later, said, "I loved getting the opportunity to chew the scenery a little bit." (Star Trek Monthly issue 37, p. 44)
- Robert Duncan McNeill enjoyed donning the prosthetics for Paris' hyper-evolved appearance. "It was fun to put on the makeup," McNeill stated. (The Official Star Trek: Voyager Magazine issue 11) He also commented, "I loved getting the opportunity […] to wear some prosthetics and turn into a lizard! That was a lot of fun." (Star Trek Monthly issue 37, p. 44) On each of the days in which McNeill played the mutated Paris, it took more than five hours for the foam latex prosthetics to be applied to McNeill. Removing the makeup was a much easier affair, however, as – unlike the alien-looking regulars of the series (such as Roxann Dawson as B'Elanna Torres, Tim Russ as Tuvok and Ethan Phillips as Neelix) – McNeill could simply rip off his prosthetics, since they were not required for reuse. (Cinefantastique, Vol. 28, Vol. 4/5, p. 94)
- The transformation scenes in which Robert Duncan McNeill played the mutating Paris were shot over a period of five days. (Cinefantastique, Vol. 28, Vol. 4/5, p. 94)
- To create the amphibious hyper-evolved Humans that Paris and Janeway mutate into, at least one full-size model was made of each of the two versions of the creatures, and the newborn versions were additionally visualized using CGI. (Red Alert: Visual Effects Season 2, VOY Season 2 DVD special features)
- The amphibians were modeled on real water-faring animals, so that the newborn versions would look appropriate when they enter water. Visual effects producer Dan Curry explained, "We had a scene where the babies were jumping in the water. And what we did there, so we could have the water interact properly with the creature, is I designed the creature like a baby seal and a reptile." (Red Alert: Visual Effects Season 2, VOY Season 2 DVD special features)
- At least one of the models of the larger amphibians was fully automated from its interior. Dan Curry remarked, "The most interesting thing for that is when they became lizards, that we had a little person inside a very large, constructed, physical lizard-like creature. And I was amazed that she was able to move around in there and get it to look so lively." (Red Alert: Visual Effects Season 2, VOY Season 2 DVD special features)
- In the sequence wherein the newborn amphibians enter water, a sock was used to act as a substitute for the CGI that would later be used to represent the creatures. "We made a black sock filled with sand about that size and dragged it, with mono-filament, into the water so the water would splash," Dan Curry recalled. "And because it was black, you didn't really see it very well. And then we would replace the black sock with a CG creature, so that it looked like the creature was actually making physical contact with the water even though it was just a cloth stuffed with sand. But it gave it the right amount of weight and mass to make the water spread from its arrival." (Red Alert: Visual Effects Season 2, VOY Season 2 DVD special features)
- This episode achieved a Nielsen rating of 6.2 million homes, and a 9% share. It was the third most watched episode of Voyager's second season (on first airing).
- Despite this, the episode proved to be highly unpopular among viewers. Shortly after the installment first aired, Jeri Taylor remarked, "We're taking a lot of flak for that. There's been a real lashing out. I recognize that people who are on the Internet and who write us letters are a tiny portion of our audience, but when it is as overwhelming as it was on this episode, you begin to take notice." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages)
- In 2003, seven years after having written the installment, Brannon Braga said, "It's a terrible episode. People are very unforgiving about that episode. I've written well over a hundred episodes of Star Trek, yet it seems to be the only episode anyone brings up, you know? 'Brannon Braga, who wrote 'Threshold'!' Out of a hundred and some episodes, you're gonna have some stinkers! Unfortunately, that was a royal, steaming stinker." (VOY Season 2 DVD "easter egg")
- At the 2009 New Jersey Star Trek convention, Kate Mulgrew remarked to the audience that "Threshold" was the episode of Star Trek: Voyager she was most uncomfortable with, noting that she didn't like the thought of mating with Paris as a lizard. 
- This episode was also panned by critics, frequently being voted as the worst ever episode of Star Trek: Voyager and even the worst episode of Star Trek in general. (Delta Quadrant, p. 97)
- Cinefantastique rated this episode 1 out of 4 stars. (Cinefantastique, Vol. 28, No. 4/5, p. 92)
- Star Trek Magazine also scored this episode 1 out of 5 stars, defined as "Total gagh!". Additionally, Stuart Clark, a reviewer for the magazine, stated that the episode "doesn't really quite gel." (Star Trek Monthly issue 15, pp. 60 & 61)
- The unauthorized reference book Delta Quadrant, (p. 97) gives this installment a rating of 4 out of 10.
- The book Star Trek 101, by Terry J. Erdmann and Paula M. Block, cites this episode as the Star Trek: Voyager winner of the "Spock's Brain" Award and states that, of the entire Voyager series, this installment is the one "most likely to give Darwin a migraine."
- Indeed, from the earliest response to this episode up to the present day, the episode has repeatedly been accused of being scientifically flawed. Robert Duncan McNeill noted, "Some of the fans sort of questioned the science of it." (Star Trek Monthly issue 37, p. 44) In the interview that Jeri Taylor gave shortly after the episode's first broadcast, she said of the negative initial response to the episode, "Some of this anger was misplaced, I thought. A lot of the ire seemed to be caused by the fact that we stated no one had ever gone warp ten before, and people flooded us with letters saying, 'That's not true, in the original series they went warp twelve and warp thirteen.' We should have had a crawl before the episode explaining all this, but it really was a recalibration of warp speed." Of the depiction of Human de-evolution, Taylor commented, "It is not one that took with the audience. The fact that we were turning people into salamanders was offensive to a lot of people and just stupid to others." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages)
- In Rick Sternbach's on-line newsgroup (posted on 17 March 1999), Sternbach referred to this installment as "the silly Warp 10 episode" and offered a highly technical reinterpretation of the episode's events. 
- Despite its lack of popularity, this episode of Star Trek: Voyager was one of only a few that were commemorated by Playmates Toys, with the launch of an episode-specific Voyager action figure release. In this case, the release was an action figure of the episode's hyper-evolved Tom Paris, complete with a phaser and his three mutant offspring.
- Furthermore, the episode won an Emmy Award for Outstanding Makeup for a Series; Robert Duncan McNeill noted that putting on his makeup here "helped them win an Emmy." (The Official Star Trek: Voyager Magazine issue 11) This episode beat out DS9: "The Visitor", which was nominated in the same category.
- During the fourth season of Star Trek: Voyager, Robert Duncan McNeill hoped for more opportunities where, like in this installment, he could expand his range as an actor. "I'd actually like to do more of that kind of thing; I'd like to see Paris have some really wild experiences in the future." (Star Trek Monthly issue 37, p. 44)
Continuity and trivia
- The title of this episode was also used for a show that Brannon Braga executive-produced nine years later (see Threshold).
- After the flight, Tom Paris was found to breathe a mixture of nitrogen and acid dichloride gas. "Acid dichloride" is not a common chemical name, but it could refer to phosgene, which has two acid chloride functional groups.
- The ability to reach warp 10 represents the fifth time besides the series premiere (after "Eye of the Needle", "Prime Factors", "The 37's" and "Cold Fire") that the Voyager crew has a possibility of returning home.
- This episode marks the first appearance of the Class 2 shuttle on the series.
- In 2018, an anonymous contributor name "BioTrekkie" submitted a fake science paper entitled "Rapid Genetic and Developmental Morphological Change Following Extreme Celerity" describing Paris' experiment in other words, to several "predatory" science journals. Four accepted it and one published it.  
Video and DVD releases
- UK VHS release (two-episode tapes, CIC Video): Volume 2.6, 8 July 1996
- As part of the VOY Season 2 DVD collection
Links and references
- Kate Mulgrew as Captain Kathryn Janeway
- Robert Beltran as Commander Chakotay
- Roxann Biggs-Dawson as Lieutenant B'Elanna Torres
- Jennifer Lien as Kes
- Robert Duncan McNeill as Lieutenant Tom Paris
- Ethan Phillips as Neelix
- Robert Picardo as The Doctor
- Tim Russ as Lieutenant Tuvok
- Garrett Wang as Ensign Harry Kim
- Andrew English as a security officer
- Brian Donofrio as science division officer
- Tarik Ergin as Ayala
- Louis Ortiz as Culhane
- Susan Rossitto and Cindy Sorenson as the hyper-evolved Paris and Janeway
- CGI as Hyper-evolved offspring
acceleration; acidichloride; allergy; alloy; alveoli; AMU; antiproton; Armstrong, Neil; asteroid field; atrophy; auxiliary power; bedroom; bio-suppressor field; brain hemorrhage; cell; centimeter; cerebellum; Class 2 shuttle (hologram); Cochrane, Zefram; Cochrane; coffee; commendation; critical velocity; cubic centimeter; cup; dark-matter nebula; dilithium; dilithium matrix; DNA; duranium; duty station; electrolyte; engineer's assistant; epitaph; evolution; flight plan; fuselage; genie; gigaquad; heart; hour; Human; hyper-evolution; hyper-evolved Human; hypothalamus; internal organ; interstitial fluid; isolation field; isotropic restraint; Kalavian biscuit; Kavarian olive; Kazon; Klingon; level 3 security alert; liver; lucidity; lungs; lymphatic system; Maquis; medical tricorder; microfracture; mitosis; multispectral subspace engine design; mutation (genetic mutation); nacelle pylon; neural stimulator; nitrogen; olive; oxygen; parsec; Paris, Owen; Paris Delight; pepperoni; percent; pizza; plasma conduit; quantum surge; quantum warp theory; rads per second; rate; Sector scanned by Tom Paris; serotonin; shuttle log; space; space door; star chart; stellar cartography; subspace torque; subspace stress; surgical bay; synaptic pattern; technobabble; telemetry; Theory of Infinite Velocity; Trabalian freighter; traitor; transwarp; transwarp drive; transwarp threshold; tritanium; velocity indicator; vestigial organs; virginity; warp 10; warp factor; warp field; warp threshold; water; Wright, Orville; year
- "Threshold" at StarTrek.com, the official Star Trek website
- "Threshold" at Memory Beta, the wiki for licensed Star Trek works
- "Threshold" at Wikipedia
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