Carnal Excitation(1978)

Original title: Excitation au soleil

A couple prepares to welcome a friend and his new fiancée, but when an unexpected guest arrives ahead of them, a case of mistaken identity sets everything in motion. As assumptions blur and boundaries loosen, the household quickly slips into a web of flirtation, confusion, and shifting dynamics. When the real fiancée finally appears, nothing is quite as it seems.. and the evening takes a series of surprising turns.