After the establishing shot of Montluc prison, but before the opening credits, the camera rests on a plaque commemorating the 7,000 prisoners who died at the hands of the Nazis.
Sir Ernest Pease (James Robertson Justice) is a brilliant but acerbic scientist working on aircraft research during World War II. He needs to take a trip on a bomber to observe the results of his work. At first the plan is to fly in an RAF plane disguised as an RAF officer, but when he is told to shave off his beard he refuses and gets to go as a Royal Navy officer, as beards are allowed in the RN.
At a Prisoner of War (POW) camp for Germans in the north of Scotland, Kapitän zur See Willi Schlüter (Helmut Griem) - a German submariner – challenges the authority of the camp’s embattled Commanding Officer, Major Perry (Ian Hendry). British Army Captain Jack Connor arrives to investigate what's happening at the McKenzie POW Camp.
Paris Pitman has pulled off a $500,000 robbery and is the only one who knows where the money is hidden. He is seen in a bordello and is captured, tried, convicted and sentenced to an Arizona penitentiary.
A cleverly planned escape attempt, which seemed guaranteed to work, ends in disaster: the would-be escapee is caught and killed by sadistic Capitano Benucci (Peter Arne) within seconds of leaving the POW camp. This incident is witnessed by the other prisoners, who notice that Benucci seemed to be waiting for the escapee to arrive before shooting him dead in cold blood.
British Captain Fred Allison (Leslie Howard) bids farewell to his new wife, Monica (Margaret Lindsay), whom he has only known for six days, and sets out for the war. He ends up a prisoner of war (POW), tortured by the fact that his wife has not written to him since the early days of his two year captivity.
Teenager Jackie Knowles (Richard Attenborough) drives a getaway car in a robbery. He is captured and sentenced to serve three years in a borstal institution run by a sympathetic governor (Jack Warner). He befriends Alfie (Dirk Bogarde) and Bill (Jimmy Hanley).
Bill et Arnie Judlow (Jack Palance) sont frères jumeaux. Marié à Ruth (Barbara Lang ), Arnie, un ancien boxeur professionnel, tue un homme par jalousie et se retrouve emprisonné à la prison d'État de San Quentin. Son frère et sa femme vont s'unir pour l'aider à s'évader. Dans leurs préparatifs, ils sont repérés par un voisin qui travaille à la prison, Henry Nova (Harold J. Stone), ce qui va compliquer leurs plans.