Body Double
(1984)

"Sam Bouchard" (Gregg Henry) is the "Indian" and he's really Alexander Revelle, Gloria's husband. In the mask of the "Indian", he killed his rich wife Gloria (Deborah Shelton). Gloria's regular erotic evening show at the window was actually performed by Holly Body (Melanie Griffith), who was hired by "Sam Bouchard" as body double for his wife Gloria, to have Jake Scully (Craig Wasson) as a witness of the later murder by the "Indian", to avoid police suspecting Gloria's husband. Jake is able to kill "Sam Bouchard" and save Holly, and get rid of his claustrophobia.

Thanks Tilman!