When his young son is killed in a hit and run accident, Charles Thenier resolves to hunt down and murder the killer. By chance, Thenier makes the acquaintance of an actress, Helène Lanson, who was in the car at the time of the accident. He then meets Helène’s brother-in-law, Paul Decourt, a truly horrible individual.

Insurance executive Charles suspects his wife Hélène of playing the field, so he has a private detective locate his wife's lover, author Victor Pegala.