An Army sergeant's photographic memory puts him in conflict with a Nazi spy.

At U.S. Army Camp Carver, Sgt. Dorian "Dodo" Doubleday is among a group of candidates for promotion to lieutenant, and has therefore earned the hostility of his rival Sgt. Ames, a physical brute who lacks Doubleday's intelligence. Ames and Doubleday are each assigned to head a platoon, and Ames thinks he has outsmarted Doubleday when he gives him a platoon of Black Mountain hillbillies. Doubleday proves his superiority over Ames by drawing upon his photographic memory and speaking the colloquial "language" of the mountain people, who immediately follow his orders. Doubleday also gets credit because his soldiers are crack shots, although they learned their marksmanship skills during their country childhoods. Doubleday's platoon is assigned to act as military police in the nearby town on payday. In addition to keeping order among the soldiers on leave, they are to ensure that soldiers do not discuss their troop movements. At a party for soldiers hosted by wealthy Dick Benedict, Doubleday's new girl friend Joan discovers microphones tucked into the flower arrangements. Joan telephones Doubleday to tell him that Benedict is a spy, then is taken hostage by Benedict and his thugs. A brawl erupts when Ames and the military police come to her aid, and Doubleday arrives in time to capture Benedict and his female cohort, Lydia. When Doubleday overhears a radio announcement of Nazi spy meetings, he memorizes the dates and locations, but Benedict knocks him out. Doubleday revives at the camp hospital but suffers from amnesia. When Ames overhears a doctor saying that another knock on the head might restore Doubleday's memory, Ames complies, and Doubleday immediately recites the enemy maneuvers.