It all starts when Kirk, Spock, Bones, Scotty, Chekov and Lt. Arlene Galway (A Redshirt who knows how to rock a pixie cut and a blue mini dress) beam down to Gamma Hydra IV to check up on a colonization party. It looks as though everyone died of old age, though they haven't been there that long. They find a couple still alive who claim to be in their late twenties, but they look positively ancient. The couple is brought aboard the Enterprise for examination, but little can be done for them. It becomes even more imperative to learn how to halt this Rapid Aging when the landing party begins to do the same. Commodore George Stocker moves to have the rapidly aging Kirk relieved of duty- and transferred to him, seeing as how all other senior officers are likewise suffering. He holds a hearing where the crew is forced to admit that, yes, Kirk's absent mindedness has been affecting his ability to command. Stocker takes command and drives the ship straight into the Romulan Neutral Zone. Fortunately, Bones has discovered the antidote just in time and Kirk is ready to save the day.Fun fact: Felix Locher, who plays the prematurely aged Robert Johnson, is in fact the oldest person ever to appear in Star Trek, born in 1882. He had turned 85 years old a few weeks before his scenes were shot for the episode. (Robert's wife Elaine was played by the much younger Laura Wood, born in 1901 - though this was Wood's second appearance as a prematurely aged character on the show, following a brief but memorable scene in "Charlie X".)
Tropes for this episode include:
- Afraid of Needles: There was a subplot where Chekov was reluctant to being poked and prodded in hopes of finding a cure. Unfortunately, these scenes are cut from the syndicated version of the remastered episode. They are intact on the DVD.
- Ass Pull: In-universe; in a Call Back to "The Corbomite Maneuver", Kirk convinces the Romulans that the Enterprise will explode if continuously fired upon, also taking out all ships in area. Chekov can hardly contain his giggles.
- Bluff the Eavesdropper: Kirk orders Uhura to send the message about the Corbomite in a code already broken by the Romulans.
- Chekhov's Gun:
- One of the signs of Kirk's mental deterioration is forgetting that the Romulans have broken Code 2. After he recovers, he uses the fact to bluff the Romulans.
- Chekov's Freak Out upon discovering the dead body ends up providing the secret to countering the radiation.
- *Crack!* "Oh, My Back!": After his gratuitous Shirtless Scene, Kirk realizes his back hurts and goes to see Bones about it. He's shocked to hear that it's advanced arthritis.
- Due to the Dead:
- When Robert and Elaine arrive and see the landing party gathered around the corpse, Robert (too far gone in senility to understand the situation) remarks that they've "come to pay their respects to Alvin".
- Bones doesn't have to say "He's dead, Jim" when Robert Johnson does it. He just pulls a sheet over his face.
- Girl of the Week: Dr. Janet Wallace is an Old Flame of Kirk's. Unfortunately for him, she has since married. And been widowed (Kirk sent her a "star-gram" of condolence, his only communication with her since their breakup more than six years earlier).
- Grumpy Old Man: Bones becomes one. Of course, it helps that he started as a grumpy middle aged man. Kirk shows signs of this as his command was taken away. Spock becomes a mild one as he complains incessantly about being cold.
- Hard Work Montage: A brief one to show Bones, Dr. Wallace and Nurse Chapel all hard at work trying to make an antidote.
- He's Back: It's all over everyone's faces when a cured Kirk takes back command of his ship.
- The Immune: Chekov is the only one not affected at all. Spock's comparatively mild afflictions are explained away by Vulcan physiology, but Chekov hasn't been affected at all.
- Improbable Antidote: Good old fashioned adrenaline!
- Insane Admiral: Commodore Stocker is perhaps the first, but certainly not the last...
- Jerkass Hasa Point : Even if Commodore Stocker is an incompetent captain, he's right : Kirk isn't in condition to command the Enterprise.
- Loving Details: Dr. Wallace knows (almost) exactly how long it's been since she last saw Captain Kirk: "Six years, four months, and an odd number of days. You mean you don't know?"
- Oh, Crap!: When the Romulans attack the Enterprise, the look on Stocker's face plainly says, "Oh, crap, what do I do now?"
- Overnight Age-Up: The basis of the plot.
- The Plague: An unknown disease causes...
- Rapid Aging
- Red Shirt: Lt. Galway is a rare (at least, for TOS) female example of this trope. Technically she has a blue science uniform, but she otherwise fits this trope as standard.
- Russian Guy Suffers Most: Possible inversion since Chekov isn't affected at all. Played straight when he becomes annoyed at the uncomfortable tests being performed to find out why he's immune.Chekov: "Give us another sample, Chekov." "A little won't hurt, Chekov." "Roll over, Chekov." "Breathe deeply, Chekov." "Blood sample, Chekov; marrow sample, Chekov; skin sample, Chekov." If—if I live long enough, I'm going to run out of samples!
Sulu: You'll live.
Chekov: Oh, yes, I'll live, but I won't enjoy it!
- Scare Chord: Played when Chekov first sees a dead and shriveled body on Gamma Hydra. Later, it's revealed that he's lucky that he was scared. The adrenaline rush protected him from rapid aging.
- Senior Sleep Cycle: Kirk falls asleep in his command chair. Bones needs to be prodded awake to give testimony during Kirk's competency hearing.
- Shirtless Scene: For some reason, Kirk just likes answering the intercom in his quarters with no shirt on. Fortunately, it's just before he starts having signs of aging, so he's still Mr Fan Service.
- Too Dumb to Live: Stocker, who nearly gets the ship destroyed by Romulans.
- Unfinished, Untested, Used Anyway: The adrenaline serum. With the Romulans threatening the ship, they really couldn't wait to test it properly.
- Younger Than They Look: Robert and Elaine Johnson, and soon the bulk of the landing party.
- You Won't Feel a Thing: Chekov was assured this before the testing. Was he told this when they performed a scenectomy for the remastered episodes?