When an unidentified alien destroys three powerful Klingon cruisers, Captain James T. Kirk returns to the newly transformed U.S.S. Enterprise to take command.

In the 23rd century, inhabitants of a domed city freely experience all of life's pleasures — but no one is allowed to live past 30. Citizens can try for a chance at being "renewed" in a civic ceremony on their 30th birthday. Escape is the only other option.