La Rocca (Jean-Paul Belmondo) is an ex-convict trying to lead an honest life. When he helps a friend who is framed for a crime, both men end up in jail. The convicts are ordered to dig up old land mines buried during the last war. La Rocca is saved by his friend, who loses an arm lending a hand to him. The two serve out their prison term and plan to buy a quiet farm. La Rocca redoubles his efforts to go straight, but his friend falls in with a blackmailing scheme.