Mirror, mirror: Kirk, McCoy and Uhura find themselves aboard a parallel U.S.S. Enterprise after an ion storm causes a transporter malfunction. Kirk and company must find their way home before they are discovered by the unprincipled barbarian crew. The deadly years: On a routine mission to Gamma Hydra IV, Kirk and a landing party are exposed to a fatal disease which causes accelerated aging. All of the landing party but Chekov are affected. With the leadership of the U.S.S. Enterprise now in the hand of arthritic, cantankerous old men, passenger Commodore Stocker assumes command. But he takes the wrong course, violating the Romulan Neutral Zone, and the U.S. Enterprise is under attack. Can McCoy find a remedy before the Romulans destroy them?