Captain Frédéric Caïn has been assigned a new lieutenant: Lucie Delambre. He multiplies his provocations to scare her away. They are investigating the murder of a young woman found burnt to a crisp in her car. A young writer with an unbridled sexuality, she had many conquests and amorous adventures. But she was also very close to a middle-class woman with a well-ordered life.

A young woman, Barbara Simon, comes to report the accidental death of her physically handicapped husband, who fell down the stairs. Cain, who has fallen under the widow's spell, is the only one not convinced of the accident theory. At the same time, Lucie is investigating the violent death of a young drug dealer and finds a way to take revenge for Cain's attitude.

Cain and Julie are called to a road accident in which the driver has died; a convertible has gone off the road on a ledge and hit a tree.

The dismembered body of a woman is discovered in a rubbish dump. It could be Anne Sentori, wife of Pierre Sentori, rugby star and Cain's idol.

The police take in an elegant 50-year-old man whose suit is stained with blood. The man can't explain the stains, and for good reason: he appears to be suffering from Alzheimer's disease.

Two cases collide for the investigators. On the one hand, a 40-year-old man, completely naked and visibly confused, reports the death of his "moms".