A French woman mourning over the death of her husband three years prior is courted by a Swedish co-worker.

From his locksmith's shop, a simple guy dreams of becoming a crime boss, at the wheel of his Cadillac surrounded by blonde bimbos. He starts small, assassinating petty criminals. Gaining renown in the newspapers as "Le Furet" (The Ferret), he soon sets his sights higher. The police and organized crime both take up the chase.