Jacques Becker co-writes and directs this French crime drama adapted from José Giovanni's novel. Wrongly convicted of the murder of his wife, Gaspard Claude (Marc Michel) is sent to Paris's notorious Sante Prison, sharing a cell with four hardened criminals. Gaspard soon learns that his new cellmates have been planning a prison break and have begun digging a tunnel in an ambitious attempt to escape. However, despite initially going along with the plan, Gaspard begins to have second thoughts when the guards inform him he is to be released soon.