The crew of the U. S. S. Enterprise is exploring the seemingly peaceful and uninhabited world of M-3107 when a bizarre and inexplicable transporter accident causes both Captain Kirk and Dr. McCoy to vanish completely. Transporter records suggest that the two men were transported somewhere, but their ultimate destination remains a mystery. Now in command of the Enterprise, Spock dispatches a search-and-rescue team -- consisting of Security Chief Giotto, Transporter Technician John Kyle, and Chief Helmsman Hikaru Sulu -- on an urgent mission to recover the missing officers. But then the rescue team disappears as well!