Nico is a burglar who sneaks into buildings and steals jewels. Nico is always followed by a black cat. The following morning, the cat wakes in a house with a little girl, catches a lizard and gives it to the girl. Zoé, hearing Jeanne, her mother, calls her to come in and look at her lizards, but Jeanne is too busy on the phone to take much notice of what she is shown. At nightfall, the cat leaves and goes to find Nico. Nico gives the cat a fish-shaped bracelet, which it gives to Zoé. Her mother sees the bracelet and asks Zoé to give it to her. Before leaving, Zoé sees a picture in her mother's dossier of a man called Victor Costa. Jeanne takes the bracelet and gives it to Lucas, a colleague of hers at the police station, who asks her to see if it matches up to any of the items stolen at one of the most recent burglaries in the Rue Mouffetard. Jeanne is commissioned to handle the security of a huge African statue that has been the target of M. Costa and that cost her husband his life. The statue is being moved soon and will be the last opportunity for Costa to get his hands on it...