Radiation on Gamma Hydra IV made Kirk, Spock, McCoy and Scott age at great speed, while Commodore Stocker took command and led the Enterprise into the Romulan Neutral Zone.
In 2267 a landing party visiting a research colony on Gamma Hydra IV found its members dying of old age. Kirk, Spock, McCoy and Scott began aging rapidly too, but Chekov, who had been badly frightened by a corpse, was unaffected. Kirk's memory began to fail, and a competency hearing removed him from command. Commodore George Stocker, a passenger with no command experience, took over and set a direct course through the Romulan Neutral Zone.
The Enterprise was attacked by Romulan ships. McCoy found that adrenaline was the key to a cure, and the restored Kirk used a bluff about corbomite to escape.