Witnesses

One winter morning, 15 frozen bodies are found inside an abandoned bus on the edge of a country road in the north of France.

Sandra discovers a pattern in the investigation. Ten years ago, a man was found dead in an abandoned bus.

The body of a young woman is found at the foot of a wind turbine. Sandra learns that Catherine attended a swingers network on the Internet.

Sandra refuses to be put under protection. Escaping the surveillance of her team, she continues her investigation solo.

Martin concedes to take Sandra and Catherine to the location where the killer locked up his first victim.

Upon discovering an old photo of an orphanage, Sandra's investigation leads to a certain Pierre Altman.