Obsession, sex, and illusion are depicted in a series of parallel stories. The Lost Door opens while Kristina is being interrogated in a psychiatric hospital where she has been committed. Catherine, a young psychiatrist has been assigned by the court to discover what goes on in the deranged yet intriguing mind of this suspected murderer, haunted by ghosts and strange sexual situations. After a long confrontation, it's the mysterious Kristina who opens up the young psychiatrists mind to her own repressed desires.

Roy Stuart started as photographer, but later made documentary movies as well, such as “Glimpse”. His photographs often deal with the female body. In The Fourth Body we apparently see him at work. Not that we see much of the photographers, the movie concentrates on females. Sometimes they are dressed, usually they are undressed. We see a few hardcore scenes being recorded, but usually we see females on the set. Many of these sets are either artsy, weird or fascinating. There are also shorts scenes of the changing of the guard in Copenhagen. This movie is not a movie in the traditional sense, for no real story is told. In fact it is more or less a collage of moving photographs.