The Sinners (1976)

Actress Sanaa Kamel is found murdered on her bed, and an investigation starts, taking into account everyone of the guests she hosted at her apartment the night she was killed: her jealous fiancé, a school instructor, a corrupt market manager, one of Sanaa's friends who works as a contractor, and a stud who was Sanaa's secret lover. As the investigation progresses, all the conclusions about the characters are always under question.