Original air date: November 10, 1967
Kirk, Spock, Bones, and our Girl of the Week, Nancy Hedford, are flying around on the Galileo shuttlecraft. Nancy is some Federation bigwig and apparently also a 1960s mod fashion aficionado. She was on an important mission when she contracted a rare space disease and is being brought to the Enterprise so McCoy can fix her right up again. But, of course, something goes wrong. No sooner has Kirk told Hedford that they'll get her back to her mission in no time, the shuttlecraft gets zapped by a Negative Space Wedgie and pulled off course. It's like nothing Kirk and Spock have seen before! Like all Federation officials who get stuck in unfortunate situations with Enterprise crew members, Hedford immediately starts acting demanding and unreasonable.
The Galileo gets deposited on some planet. Kirk and Spock can find nothing wrong with the shuttlecraft and yet nothing works. Suddenly, a man runs in wearing an orange jumpsuit. As we will learn later, he is Zefram Cochrane. Yes, that Broken Pedestal guy who will invent warp drive in Star Trek: First Contact. Or rather has already invented warp drive in... no, that's not right either. He now looks a lot younger than he did when he flew the Phoenix, but this actually gets explained. He introduces himself as just "Cochrane" (still doesn't like being a hero apparently) and flirts with Hedford. Explaining that he's been marooned on this planet for ages, he offers them his hospitality with an offer of a hot bath directed specifically at Hedford. She shuts him down with The Power Of Sarcasm. Evidently he hasn't gotten any more subtle since the drunk Troi days. Cochrane takes them all to his settlement, where Kirk, Spock, and Bones see the entity which brought them to the planet. After failing to convince them that it's a hallucination, Cochrane admits that "the Companion", as he calls it, brought him to the planet and rejuvenated him, as he was an old man near death. This effectively resolves a Plot Hole which won't exist for thirty years, but there's a less resolvable plot hole coming up. He admits to being Zefram Cochrane and Kirk asks "Of Alpha Centauri? The discoverer of the space warp?" Cochrane agrees, apparently too lazy to say "That's Bozeman, Montana. Don't you know where First Contact happened, genius?" In any case, McCoy gasps that Zefram Cochrane died a hundred and fifty years ago, but Spock concedes that they Never Found the Body. Cochrane reveals that he can communicate with the Companion and that it brought the rest of them there because he complained about being lonely. Trouble is, Nancy is now dying of overacting and McCoy says she only has hours left.
Kirk orders Spock to create a viable weapon to use against the Companion. Cochrane agrees to cooperate, admitting that "immortality consists largely of boredom". Kirk figures that the Companion might be able to cure Hedford, so he gets Cochrane to ask it. It turns out Cochrane and the Companion communicate with each other using some kind of nonverbal symbiosis. Unfortunately, the Companion can't do anything to help Hedford. Yes, rejuvenating a near-death 87-year-old man into a thirties-looking guy is a piece of cake for this Companion thing, but it's out of the question for it to cure the same disease which McCoy says he could cure in a jiffy if he only had the equipment in Sickbay. Meanwhile, Spock determines that the Companion is mostly electricity, so he creates a device to scramble it. Cochrane fears this may kill the Companion, but he reluctantly goes along with it, though not without throwing a guilt trip at Kirk. However, the device only succeeds in making the Companion mad. McCoy does his thing by suggesting that they try to reason with the entity instead and Kirk tells Spock to modify a Universal Translator. Meanwhile, the Enterprise reaches the point where the shuttlecraft was grabbed by the Companion. Back on the planet, Kirk talks to the Companion with the universal translator. When the translator gives the Companion a woman's voice, Kirk realizes it must be a female. It's immediately presumed that this means the Companion is in love with Cochrane. Kirk tells the Companion that they need to leave or one of them will die, but she says they need to stay to keep her dear Zefram company and refuses to hear of any holes in this plan.
But for the past one hundred and fifty years, Cochrane has been Oblivious to Love and failed to notice that his best friend was a girl (typical guy). Cochrane insists that She Is Not My Girlfriend and McCoy replies that Everyone Can See It. But for Zefram, it's drunk ship's counselors and islands of naked women, thank you very much! The Companion's just not his type and he storms away. Nancy, however, seems to be jealous of Cochrane for being loved as she is Married to the Job and seems to regret that now that she's dying. Kirk talks to the Companion again and plays the "if you really loved him" card. He ends up telling her that she can't properly "join" with Cochrane anyway since their forms are incongruous. This prompts the Companion to join herself with Hedford, curing her of her disease and making them one being. Spock mentions that the Companion can't create life and Hedford/Companion replies that "that is for the maker of all things". So... Carol Marcus then? In any case, this means she no longer has the power to keep them on the planet, having given it all up because she is such a Love Martyr. Kirk contacts the Enterprise, which apparently happened to follow the right course, and Sulu lays in a course for the planet. When Hedford/Companion tells Cochrane that she can never leave her planet, he chooses to stay. Kirk points out that there is a whole galaxy out there waiting to honor him. Yeah, great idea, Kirk. Cochrane just loves it when people make a big deal out of his accomplishments. Giving Cochrane his word that he won't tell the galaxy what became of him, Kirk takes the shuttle back to the Enterprise with Spock and Bones.
- All Gravity Is the Same: Spock comments on the absurdness of a planetoid that size having Earthlike air and gravity. It's presumably caused by the Companion's power but they don't all float into space when she's Brought Down to Normal at the end.
- Artistic License – Biology: Kirk claims that male and female are universal constants. That must come as news to all the hermaphroditic species out there, of which Earth alone has thousands.*
- Call-Forward: An unintentional one; in spite of a century and a half of isolation, Cochrane immediately recognizes Spock as a Vulcan. This was (in part) the inspiration for bringing the Vulcans in at the end of Star Trek: First Contact.
- Does This Remind You of Anything?: Beyond sixties heteronormativity, Cochrane's reaction to the companion being female is one of disgust, and accuses the boys of being disgusting for being alright with it, a lot like he's just been told a man is in love with him.
- Early-Installment Weirdness: We're introduced to Zefram Cochrane, whose backstory would be heavily retconned by the time we met him again in First Contact. For instance, Kirk says he's of Alpha Centauri, while he would later be shown to be from Earth. In addition, Cochrane only discovered warp drive for humans; other species discover it on their own. So in a sense the weirdness is on the part of the Next Generation.
- Exposition of Immortality: Kirk notices the "antique" instruments from Cochrane's ship, and doubts that they're from a ship that crashed only a few years ago as Cochrane's apparent age indicates.
- Grand Theft Me: The Companion takes over Nancy's body when she's dying, stating "we are one" but there doesn't really seem to be much of Nancy left in her personality.
- Translator Microbes: This episode gives us the first appearance of the Universal Translator, and gives some detail as to how it works. It appears here as a hand-held device that Kirk talks to the Companion through, though it's indicated to have been installed in the shuttle; presumably they're usually built into the comms system.
- Stock Footage: All the footage of the shuttlecraft in outer space was reused from "The Galileo Seven", some with the Companion animation added in post-production.
- Stumbling Upon the Lost Wizard: Lost scientist Zefram Cochrane, inventor of the warp drive, is discovered by the Enterprise. He has an otherworldly companion that allowed him to live for centuries, not unlike the fey servant of the Ur-Example of this trope, Prospero.
- Who Wants to Live Forever?: The central theme of the episode. Being trapped in one location as a prisoner with eternal life without being allowed to experience anything is considered no different from death.