A young commissioner investigates the murder of a girl, which took place the previous night in a tram carriage. In order to solve the case, the commissioner is willing to do anything, even to jeopardize the life of his girlfriend.

A patient in a psychiatric hospital appears to be the perpetrator of a homicide. The police try to track him down, while a girl who is trying to steal a doll comes across an ambiguous individual.

The constant sensation of imminent danger and the "black" climate typical of Dario Argento's production: in the last episode, a woman tells of having witnessed a murder, but, having no evidence to provide, she is not believed.