Series: Star Trek: The Original Series
Season 2, Episode 12
Original Air Date: December 8, 1967
A stop at Gamma Hydra IV proves disastrous for the Enterprise crew. Intending to resupply a research station on the planet, our heroes find all of the scientists to be rapidly aging and dying. Upon returning to the ship, most of the landing party begin aging faster as well, apparently due to radiation exposure while on the planet. The balance of the episode is devoted to reversing the effects and also questioning whether Kirk, Bones and Spock are still fit for duty when compromised mentally by the aging process.
Just for fun, let's compare the artificial aging in the episode to William Shatner's own natural course since.
|via Memory Alpha|