The quiet stillness of the Orti house, where Melissa lives with her cousin Gianni and her aunt Adele is broken by the arrival of Franca, a young "uninhibited" girl. Franca soon manages to destroy the ordered way of life of the host with her life style. The drama was born when Melissa surprised her in the company of a stranger and when the following day she discovered Franca"s death. Convinced of being the perpetrator of the crime; Melissa with the complicity of Gianni throws the corpse into the canal. The investigation undertaken by the police commissioner to whom Aunt Adele had addressed the disappearance of the young woman.