The Case of the Bloody Iris (1972)

When two young women are viciously slain in a luxury high-rise, a beautiful young model moves into one of their vacated apartments - and soon finds that she is now being stalked by the mysterious killer! The suspects include her ex-husband (a member of a group sex cult), a predatory lesbian neighbor, the deformed son of a sinister widow, and even the building's handsome architect who suffers from a paralyzing fear of blood. Can she expose the masked maniac with a taste for luscious women and depraved murder before she becomes his next victim?