Executive Producer: Gene Roddenberry
Producers: Gene L. Coon + John Meredyth Lucas
Associate Producer: Robert H. Justman
Script Consultant: D. C. Fontana

Writer: David P. Harmon
Dir.: Joseph Pevney

Captain Kirk: William Shatner
Science Officer, First Officer, Cmdr. Spock: Leonard Nimoy
Dr. Leonard "Bones" Mc Coy: DeForest Kelly
Lt. Sulu: George Takei
Lieutenant Commander Montgomery Scott: James Doohan
Lieutenant Uhura: Nichelle Nichols
Nurse Christine Chapel: Majel Barrett

Robert Johnson: Felix Locher
Elaine Johnson: Laura Wood
Lt. Arlene Galway: Beverly Washburn
Commodore George Stocker: Charles Drake
Dr. Janet Wallace: Sarah Marshall

Stardate 3478.2

Kirk, Spock, McCoy Scotty, Chekov and Lt. Galway beam down on the surface of Gamma Hydra IV on a routine mission. They find the town deserted. Chekov unexpectedly encounters a body and gets a fright. They find the people of the planet dead or dying and themselves exposed to radiation caused by a comet. The exposure makes them age rapidly – though each on it's own pace. Spock's longevity keeps him from aging as fast as the others, but he does age at a rapid sped, too. 

While Chekov is the only one not showing any signs of accelerated aging, Lt. Galway ages so quickly that she dies. On board is Commodore Stocker on his way to Starbase 10. It becomes even more painful for them as they see the others not changing at all, while they age for years in a day. McCoy becomes irritable and Kirk forgetful. Noticing this, Commodore Stocker insists in a hearing; he feels Kirk is not fit for command. Reluctantly Spock is forced to agree and Kirk's tendency to forget costs him his beloved command. Kirk becomes angry and accuses Spock of taking over by himself, but Spock declines for the same reason his captain has been dismissed. What is apparent for Kirk is apparent for him, too.

Stocker himself takes over and soon finds himself in trouble - in the Romulan Neutral Zone surrounded by enemy ships. McCoy, who's been working nonstop on an antidote, finally finds the cure while talking with Spock and Kirk, but is too weak to work on it. The amount of adrenaline in Chekov's blood, after bumping into the coffin with the body in it, was suddenly increased and preserved him from the effects of the decease. Spock and Dr. Janet Wallace work on it. Before it can be tested Kirk insists to have a dose. Seeing his ship in that situation Kirk takes over command again – from a quite relieved Stocker – to save his ship. He had regained his age he was used to in a very short time and works with the Carbomite bluff (s. # 3 The Carbomite Maneuver), the 10 Romulan ships withdraw and the Enterprise is out of jeopardy. McCoy knows that the injection causes people to fight and assures Spock that he has removed anything which can be broken (since he knows of Spock's Vulcan strength). Spock finds this action very considerate.