Eyes Behind the Wall (1977)

Ivano is a wheelchair bound man with some strange perversions. He gets his sexual kicks by spying on Arturo, his tenant in the apartment next door, while he forces his sexy accomplice, Olga, to watch as well. To increase his perverse thrill, Ivano persuades Olga to seduce Arturo and to have sex him as he watches. Unfortunately for all involved, the sex game starts to get very deadly.