The U.S.S. Enterprise, under the command of Lieutenant Hikaru Sulu, is returning from a mission to deliver medical supplies to Deep Space Station C-15, one of Starfleet's most distant installations. All is routine until the Enterprise comes within a light-year of the planet Mu Arigulon, when the ship is suddenly thrown from warp and suffers a momentary power cut, having run aground on a spatial distortion not revealed in previous scans of the system. When the pride of Starfleet hits another, much worse distortion, Dr. Leonard McCoy has his hands full caring for officers who have suddenly fallen into comas for no apparent reason. The Enterprise medical team soon discovers that the dying officers are espers—humans with a rare and abnormal level of telepathic and psychic ability. With no choice but to link to the officers' minds in order to come to their aid, McCoy is plunged into a nightmarish dream-world . . . with the end result being nothing short of the possible destruction of the Enterprise and all aboard her. . . .