The Maid Seduces the Cowards (1980)

Marina and Orazio are a couple who own a motel. To pay their debts, Marina suggests a drug-related money scheme. However, both have their own agendas and try cheating on each other with another couple. One thief hopes to get the money, but accidentally gets trapped in the chambermaid's room, where the lusty chambermaid has her way with him.