In 1943, Royal Navy Lieutenant Commander Ewen Montagu (Clifton Webb) devises a scheme to deceive the Nazis about the impending invasion of Southern Europe. It entails releasing a corpse with a fictional identity off the coast of Spain. The strong currents would almost certainly carry it ashore near where a known German secret agent operates. The non-existent Royal Marine, Major William Martin, would appear to be a plane-crash victim carrying falsified letters about a forthcoming Allied invasion of German-occupied Greece, rather than Sicily, the more obvious target. Montagu receives approval to carry out Operation Mincemeat.