Major Wright, [Telly Savalas], is summoned by [Ernest Borgnine] General Worden, who warns that the Germans have the capability to launch V-2 rocket missiles packed with deadly nerve gas to strike targets across the Allied lines. Worden orders Wright to assemble a crack team of convicts and guide them deep into occupied France, toward the monastery at Saint-Michel, with a dual mission: destroy the nerve-gas containers and rescue the scientists who could help turn the tide of the war. The stakes are immense, and time is short, as the enemy’s reach appears increasingly dangerous and precise.
Wright pours his trust into a handpicked unit he dubs the Deadly Dozen. The twelve men represent a mix of grim resolve and hard-earned battlefield experience: Joe Stern, [Gary Graham]; Eric "Swede" Wallan, [Randall 'Tex' Cobb]; Ernesto "Pops" Ferucci, [Paul Picerni]; Ronald (Ronnie) Webber and David Webber, [Vincent Van Patten] and [James Van Patten]; Maurice Fontenac, [Bo Svenson]; Martinez, [Pavle Balenović]; Francis Kelly, [Thom Mathews]; Ballews, [Pavle Balenović]; Sturdivant, [Matko Ragu]; Chacon, [Mario Barbaric]; and Spencer, [Milan Ristic]; with Hallet, [Sam Douglas], as the last addition. Their one week of tough, practical training is overseen by Sergeant Holt, [Vince Edwards], who pushes them through gritty conditioning and realism to prepare for a mission that will demand both nerve and teamwork.
Back in France, the mission’s shadow falls quickly when Colonel Krieger captures French Resistance leader Paul Verlaine, who had parachuted in with a British contact bearing news of the impending operation. Verlaine and his ally are executed, and Pierre Claudel, a monastery scientist aligned with Vichy and the Nazis, identifies Verlaine in conversation with lead scientist George Flamands, sparking Krieger’s decision to tighten security around the monastery. The tension mounts as Krieger’s patrols become more vigilant, foreshadowing the dangerous obstacles the Deadly Dozen will face.
Meanwhile, Worden returns to Wright in England with sobering news: someone inside the operation has leaked intelligence, and security has tightened. The plan shifts again; the dozen will now enter France by sea, since air routes are being closely monitored and tracked by German eyes. The clock ticks loudly as the team readies for a river approach, knowing that every moment counts and any misstep could derail the entire rescue.
Upon landing, the twelve men advance through a French forest rendezvous where they meet their contact, Marie Verlaine, daughter of Paul Verlaine, and a resilient group of resistance fighters. Marie reveals a complicating factor: the families of the kidnapped scientists have also been brought to the monastery, deepening the rescue portion of the mission. To outmaneuver Krieger’s patrols, Wright devises a river route and the team seizes a patrol boat, though not without loss—Sturdivant falls in the assault. The unit presses on and makes camp at a resistance farmhouse to rest briefly, while Major Wright and Fontenac slip into the monastery disguised as monks to confer with Flamands and map out their plan.
The pair returns to the monastery to trigger the attack, while the rest of the Dozen infiltrates the compound. The assault unfolds with a fierce clash as German troops press back. Wright disables the communications hub, and Stern infiltrates the basement in a bid to disrupt the enemy’s coordination. Fontenac acts as a crucial link, opening a back door that allows Marie, Swede, Martinez, and the resistance fighters to bring in explosives. Ferucci sustains a shoulder wound, and Chacon and Spencer are killed in the fighting. In the ensuing chaos, the group discovers not only the scientists’ families but also Flamands and his wife Julia, who have been brought to a villa for a recital hosted by a German general.
Wright makes a bold call to extract everyone, including Flamands and Julia, and orders a truck to shuttle the group toward a British evacuation plane. Decoys are deployed—two trucks driven by Martinez, Ballews, and the Webber brothers—and the real convoy heads to the rendezvous point. In a brutal turn of events, German patrols destroy the decoys and the sacrifice of the decoys costs the lives of the Webber brothers, Martinez, and Ballews. Realizing the trap, Krieger and his men race toward the landing zone, firing on the plane as the scientists and their families are loaded. Fredric Flamands panics, but Fontenac remains brave, carrying him to safety as a mortal shell wounds Fontenac, and Fredric is knocked unconscious. Wallan’s quick actions save Fredric and Kelly, and Fontenac diverts attention by drawing the enemy’s fire, buying the plane enough time to get airborne and slip away to the English airstrip.
In the aftermath, a handful of the original Deadly Dozen survive the mission: Major Wright and Sergeant Holt, alongside Joe Stern, Eric "Swede" Wallan, Ernesto "Pops" Ferucci, and Francis Kelly, who earn their freedom through grit, sacrifice, and the revenge of daring resistance against overwhelming odds. The mission leaves a lasting mark on everyone involved, underscoring the grim realities of war and the possibility that a small, tightly trained unit can alter the course of history when courage meets resolve.
