In 1942, the Third Reich moves a group of captured Allied airmen with a history of escape attempts to a new POW camp commanded by Luftwaffe Colonel Luger. He warns Group Captain Ramsey—the highest-ranking Allied prisoner and de facto leader of the group—that the POWs should give up attempting to escape.
Many of the men immediately try and fail. Hilts, a notoriously prolific escapee, finds a blind spot at the fence and purposefully gets caught so his discovery will go unnoticed. He is sentenced to solitary isolation in "the cooler" in a cell next to Ives, and the two plan to escape together. Meanwhile, Bartlett re-establishes "the X Organisation", an escape-planning committee from a former camp, with Ramsey's tacit approval. Bartlett argues that if they can break out an unprecedented 250 men simultaneously, it will force the Germans to divert significant manpower away from the front.
The POWs begin working on three tunnels codenamed Tom, Dick, and Harry.[8] Hendley secures vital objects on the black market and befriends expert forger Blythe. Sedgwick makes picks and air bellows, Welinski and Dickes oversee the digging, MacDonald gathers intelligence, Griffith sews civilian disguises, and Ashley-Pitt devises a method of hiding the excavated dirt. Digging noise is masked by a choir led by Cavendish, who also surveys the tunnels' routes. Aware that Hilts is planning his own escape, Bartlett asks him to scout out the surrounding area and then allow himself to be recaptured so he can draw maps for the X Organisation, but Hilts refuses out of pride.
As Tom nears completion, Bartlett orders Dick and Harry sealed off. Hilts, Hendley, and Goff brew potato moonshine with a homemade still and throw a Fourth of July party for the camp, but during the celebration the guards find Tom, to the prisoners' dismay. A despondent Ives snaps, scales the fence, and is shot dead. Hilts, shaken, agrees to help the X Organisation.
Bartlett orders Harry reopened. When the tunnel partially collapses, Welinski confides to Dickes that he is claustrophobic; he tries to break out through the fence, but Dickes calms him down and promises to help him overcome his fear. Blythe realises he is going blind due to progressive myopia, and Hendley takes it upon himself to be Blythe's eyes outside the camp.
The POWs complete Harry, but on the night they break to the surface they find themselves 20 feet short of the woods. With Hilts' help—and aided by an air raid blackout—dozens of men flee before Cavendish slips and makes a noise. An impatient Griffith exits the hole while a guard investigates and is captured, ending the breakout.
The 76 escapees flee across Europe but only three make it to freedom: Welinski and Dickes escape to Sweden, while Sedgwick reaches Spain. The rest are unsuccessful: Cavendish hitches a ride but is turned in by the driver. Hendley and Blythe steal a plane to fly to Switzerland but crash when the engine fails; Blythe is shot and dies as Hendley is recaptured. Hilts steals a motorcycle and heads for Switzerland but is recaptured at the border. At a train station, Ashley-Pitt kills a Gestapo officer to prevent him from apprehending Bartlett but is himself shot and killed. Later, Bartlett and MacDonald are caught when MacDonald is tricked into speaking English.
Most of the men—including Bartlett, MacDonald, Cavendish, and Haynes—are told they are being taken back to the camp, but instead are actually driven to a field and shot dead. Luger delivers news of the murders—justified by his superiors under the pretext that they were killed during the escape attempt itself—to Ramsey, who informs the returning survivors, among them Hendley and Nimmo. Hendley wonders whether the escape was worth it; Ramsey says it depends on one's point of view. Luger is relieved of command by the SS and driven away to an uncertain fate. Hilts returns to the cooler, where he starts planning his next escape.
