When the newly-christened starship Enterprise's shakedown cruise goes poorly, Captain Kirk and crew put it into Spacedock for repairs. But an urgent mission interrupts their Earth-bound shore leave. A renegade Vulcan named Sybok has taken several ambassadors hostage on the planet Nimbus III, an event which also attracts the attention of a Klingon captain who wants to make a name for himself. Sybok's rag-tag army captures the Enterprise and takes it on a journey to the center of the galaxy in search of the Supreme Being.