On a sunny spring day at the beginning of the 1970s prychiatrist Dr. Zack Busner and his fellow residents at the Concept House therapeutic community in north London drop acid. At the peak of this ill-advised (and, for some of them, not entirely voluntary) trip, Michael Lincoln, British observer on the Hiroshima A-bomb mission, arrives at the House and comes face to face with inmate Claude Evenrude, a survivor of the Japanese sinking of the USS Indianapolis in the shark-infested Pacific. As the day progresses, and the acid takes hold, the threads of consciousness of the participants unravel, and their nightmares and memories are woven into a hallucinogenic tapestry of events from which there seems neither escape nor redemption.