Captured French Resistance fighter Lieutenant Fontaine awaits a certain death sentence for espionage in a stark Nazi prison in Lyon, France. Facing malnourishment and paralysing fear, he must plot an extraordinary escape, complicated by the questions of whom to trust, and what lies beyond the small portion of the prison they are housed in. Based on the memoirs of André Devigny, a member of the French Resistance held in Montluc prison by the occupying Germans during World War II.