Jan (Mathieu Carrière), who is a young seaman, returns to land, and while searching for his childhood home, is mysteriously abducted. He awakens in an isolated old mansion called Malpertuis, where he find himself among various relatives, including his sister Nancy (Susan Hampshire), as well as a strange taxidermist and a resident madman called Lampernisse. The mansion turns out to be a labyrinth of corridors, staircases, and secret chambers, belonging to his family.