Body Double is based on a screenplay written by American director Brian de Palma and screenwriter Robert J Avrech.

Claustrophic Jake Scully (Craig Wasson) has just been fired from his acting job and gone home to find his girlfriend in bed with another man. Scully desperately needs someplace to stay and jumps at the chance to house-sit a spectacular place in the Hollywood Hills while the owner is in Europe and the current house-sitter, fellow actor Sam Bouchard (Gregg Henry), has to leave town for a five week gig. It's even more special when Sam shows Scully a telescope and points it at an open window where a beautiful brunette (Deborah Shelton) performs a erotic dance every night "just like clockwork." However, it doesn't take long before Scully realizes that the woman is being stalked by a mysterious Indian with a disfigured face and may be in danger.

Yes. The house, designed by American architect John Lautner in 1960, is known as the Chemosphere. It's on Torreyson Drive, just off Mullholland Drive, in Los Angeles, California. Photos of the house, both outside and inside, may be seen respectively here and here. Gloria Revelle's house is about two miles away on Miller Drive between Hedges Place and Miller Way, also in the Hollywood Hills. Unlike in the movie, there is no way to see one house from the other, as there are hills blocking the way.

It's not clear from the movie. Viewers have suggested it could be (1) her lover, (2) a friend, (3) her shrink, (4) her husband (i.e., trying to make peace with him), or (5) no one (in that she was trying to get Scully's attention).

Since Gloria and her husband are separated, the husband would be the first one the police would suspect should anything happen to Gloria. By having the Indian steal her keycard, it would take some of the heat off the husband, knowing that someone else was also in possession of a key.

Holly admits that it was she, not Gloria, who was doing the erotic dance in the Revelle's window and storms off, calling Scully a pervert. Scully calls Detective McLean (Guy Boyd) and tries to explain how he was set up by Alexander Revelle to be witness to the Indian murdering Gloria. It takes some convincing to get McLean to believe his story, but he eventually asks Scully to come down to the station. Meanwhile, Holly has been trying to hitch a ride and been picked up by the Indian in his Ford Bronco. At a roadblock caused by an accident, Scully looks into the Bronco and sees the Indian hit Holly with a tire iron. Scully attempts to alert the police to the fact that the guy is attempting to kill Holly, but the police seem more intent on getting Scully back into his car so that they can move the traffic along. When the Bronco finally starts to move forward, Scully runs after it, scaling a fence and following them into a reservoir yard where he finds the Bronco and the dog inside growling and barking. Scully inches forward in the dark looking for Holly but is pulled into a deep pit by the Indian. Scully tries to defend himself. In doing so, he tears off the Indian's mask to find that the Indian is actually Sam. Sam starts to toss dirt over Scully, while Scully's claustrophobia starts to kick in. Knowing that he either has to act now or die, Scully visualizes himself back shooting his role as the vampire. Rubin the director (Dennis Franz) tells him that he'd better get it right this time, and Scully forces himself to scream. The dog breaks the window of the Bronco and comes tearing at him, but Scully ducks and the dog plows into Sam instead. Sam and dog go over the edge of the reservoir into the water below. Suddenly, Holly pops up beside him but refuses to listen to his explanation, calling him a "sicko" and preferring to stay in the pit. In the final scene, Scully is back on the movie set filming the shower scene, having convinced Rubin to give him back his role as the vampire. As they change the actress (Denise Loveday) for her body double, the credits roll. Holly stands nearby watching and tells the actress, "You're going to get a lot of dates when this comes out."