Nude for Satan (1974): or, Buck Nekkid With Beelzebub
Nude for Satan begins when Dr. Benson (Stelio Candelli, Planet of the Vampires, Demons) crashes his car on the side of the road. While getting out to inspect the damage, another car crashes behind him and Susan (Rita Calderoni, Delirium) spills out injured from her car. Collecting the young lady, Dr. Benson goes to a nearby house to ask for help. When no one answers the door, the doctor begins to poke around inside where he encounters a doppelganger of Susan, now calling herself Evelyn, and she believes him to be a man named Peter. The next morning, Susan, not looking like she spent the night passed out in a car, arrives at the mansion and is met by a mysterious green eyed man (James Harris). He invites her to stay, and after a bath, Susan meets Peter who looks like Dr. Benson and thinks she's Evelyn. If you didn't follow that, don't worry, the characters have a hard time keeping up too. Eventually the real Dr. Benson and Susan meet up, and between floggings, scenes of stocking fetishism, and one really horny paper-mache spider, they attempt to make their escape. They soon begin to suspect that their host is in fact The Devil, and they've been nude for him all along.