In 1943, Lt. Cmdr. Ewen Montagu, Clifton Webb, conceives a bold deception aimed at misdirecting the Nazis about where the Allied invasion would actually begin in Southern Europe. With the backing of Winston Churchill, he pushes forward a plan that will come to be known as Operation Mincemeat.
Following medical advice, Montagu secures the consent of the deceased’s father and selects a man who died of pneumonia, crafting the illusion that the body had drowned. The corpse is sealed in a canister packed with dry ice and transported to a waiting submarine, beginning a meticulously staged course toward the Atlantic coast of Spain where it is destined to wash ashore. Local authorities, under the watchful eyes of both German and British observers, identify the body and conduct an autopsy, while the attaché case containing the deceptive documents is returned to London. A forensic examination confirms that a crucial letter describing an Allied invasion of Greece has been cleverly opened, photographed, and resealed, bolstering the ruse.
Hitler becomes convinced the documents are genuine, though the German intelligence head, Admiral Canaris, remains skeptical. The Germans dispatch Patrick O'Reilly to London, an Irish spy sent to probe the truth behind the “Martin” story. O'Reilly probes Lucy Sherwood, the flatmate of Montagu’s assistant, Pam, and the pair of women—Lucy and Pam—become part of the spy’s cautious chessboard. Lucy’s genuine grief over a fiancé lost in action initially convinces O'Reilly of the plausibility surrounding the supposed romance and backstory, complicating the investigation.
As a final test, O'Reilly sends a signal by leaving his North London address with Lucy, signaling that he might be in danger. Montagu, Michael Hordern as Gen. Coburn, and Scotland Yard’s Special Branch recognize the risk and rally to halt any misstep. When no arrest comes, O'Reilly radios a triumphant “Martin genuine!” message, and the German forces begin to shift their priorities. The result is a strategic misallocation: most of the Sicily-based troops are diverted to Greece, aiding the eventual Allied invasion of Sicily.
After the war, Montagu receives several decorations for his wartime work, including the Order of the British Empire (OBE). He travels to Spain and places the OBE medal at the grave of Major Martin—the man who never was—as a quiet tribute to the elaborate ruse that helped shorten the conflict. The operation’s legacy lingers in historical memory as a striking example of intelligence craft that shaped the course of a pivotal theater.
