Conducting a survey of a planet, a landing party from the Enterprise is contaminated with a form of radiation sickness that accelerates aging. With the ship's entire command crew rapidly aging and slowly losing their ability to perform their routine duties, Commodore Stocker, who is aboard for a trip to his next starbase command, decides he must question their competency and take the captain's chair as Kirk, Spock and the others face an impending death of old age.
