Plot
Major Wright is summoned by Major General Worden who informs him that the Germans have the capability to launch V-2 rocket missiles filled with deadly nerve gas to strike targets against the Allies. General Worden orders Wright to recruit convicts and take them deep into France to the monastery at Saint-Michel to destroy the containers of nerve gas and rescue the scientists.
Wright chooses the convicts for his Deadly Dozen: Joe Stern, Eric "Swede" Wallan, Ernesto "Pops" Ferucci, brothers Ronald and David Webber, Maurice Fontenac, Martinez, Francis Kelly, Ballews, Sturdivant, Chacon, Spencer and Hallet. They have one week of training, and with the help of Sergeant Holt, Wright begins training his men.
Meanwhile, in France, Colonel Krieger captures French Resistance leader Paul Verlaine and his British contact, who had parachuted in with news of the forthcoming mission. After Krieger has the two men executed, Pierre Claudel, a scientist at the monastery loyal to Vichy and the Nazis, identifies Verlaine conversing with lead scientist, George Flamands. A suspicious Krieger orders increased security at the monastery.
Back in England, General Worden appears and reveals the intelligence leak and increased security to Wright, and informs him that the dozen will now enter France by sea, as all flights to France were being heavily monitored.
Upon coming ashore, the dirty dozen march to their rendezvous point in the French forest, where they meet their contact, Marie Verlaine, the daughter of Paul Verlaine, and her fellow resistance fighters. Marie informs Wright that the scientists' families have been brought to the monastery, complicating the rescue portion of the mission. To avoid Krieger's patrols and checkpoints, Wright decides that they should travel by river, and the unit successfully takes control of a patrol boat, but Sturdivant was killed. They eventually making their way to a resistance farmhouse, where the men are allowed to rest, while Major Wright and Fontenac go to the monastery dressed as monks to meet with Flamands and inform him of their plans.
Wright and Fontenac re-enter the monastery to trigger the attack, while the others infiltrate the monastery compound. While the dozen battle the German troops, Wright destroys the communications center, Stern makes his way into the basement and Fontenac opens the back door allowing Marie, Swede, Martinez and the resistance in with the explosives. Ferucci is wounded in the shoulder while Chacon and Spencer are killed. The group then find not only the scientists' family, but also Fredric Flamands, George Flamands' son. The group is also notified that Flamands and his wife Julia have been taken to a recital at a villa as guests of a German general. Wright decides to take everyone with them, and that he and Stern must head to the villa to rescue the Flamands. The scientists and their families are boarded into a truck and head to the spot where a British plane is to pick everyone up. Major Wright sends the truck on a back road while sending two decoy trucks driven by Martinez, Ballews, and the Webber brothers. Major Wright and Stern, posing as German officers, enter the villa and remove Flamands and head to the rendezvous point.
German patrols destroy the decoy trucks, and both the Webber Brothers, Martinez and Ballews are all killed. Realizing they have been tricked, Krieger and his men race to the area where the plane has landed and begin firing upon it, as the scientists and their families are being loaded. Fredric panics; however Fontenac managed to carry him to safety but a mortar shell wounds Fontenac and knocks Fredric out. Wallan manages to save Fredric and Kelly. Fontenac sacrifices himself by drawing fire from approaching patrols, giving the plane enough time to be boarded and take-off before embarking back to England.
Besides Major Wright and Sergeant Holt, the surviving members of the 'dirty dozen' include Joe Stern, Eric 'Swede' Wallan, Ernesto 'Pops' Ferucci, and Francis Kelly, who earn their freedom.
