Lyon, 1943. A car driven by an SS soldier is transporting French prisoners to the prison of Montluc. One of them, Fontaine, to whom they forgot to put in handcuffs, jumps from the running car. He will be soon captured again, beaten, put in chains and locked in jail. Fontaine's charges are heavy ones. For four months, in the loneliness of his prison, he prepares a plan to escape. The only thing he has is a spoon, which has been patiently sharpened. The film is based on a true story told by André Devigny in 1954 and it is considered a masterpiece.