The crushed body of a nine-year-old boy is found in a village street, the victim of a hit-and-run driver. His father, a lonely widower of 35, has lost all that was most dear to him. He is an author of children's books and he conducts historical research. After three weeks in which there is no trace of the driver who killed his son, he sets out to find him. He puts an ad in the paper: "l am going to kill a man. I don't know his name or address, but I'll kill him."

One day, he hears of a powerful car seen parked near a river with a couple cleaning it. The woman is a well-known television personality, the man's name is Paul. The bereaved father tracks the woman down and poses as a manufacturer under an assumed name. She is interested in his money, he in vengeance. Paul is her brother-in-law, and she broke an affair with him after an accident in which a child was killed...