The FBI trails a young couple suspected of stealing government plans.

On her first day of work, secretary Evelyn Smith learns that her employer, Senator Remmy of Southern California, is involved in monitoring fugitive Nazi spy activities. At Remmy's deserted seacliff house, Evelyn, who was hired by Remmy because she claimed to have worked for a friend of his in Washington, is asked to transcribe a telephone message from investigator James Blackton. During the phone call, Blackton discovers a spy microphone dangling outside his window and tells Remmy that he will relay his findings face-to-face that day. Desiring privacy, Remmy asks Evelyn to spend the afternoon on the beach, and she happily goes for a swim. While driving along the seaside highway, former Marine sergeant Johnny Christopher spots Evelyn in her bathing suit and stops with his dog Bazooka. After stripping to his bathing suit, Johnny chats with Evelyn, but she brushes him off and returns to Remmy's house. When she walks through the front door, however, she is ambushed by two strange men. Johnny, meanwhile, returns to his car and discovers that he has locked his keys inside. He goes to Remmy's house for help, but is surprised when a sharp-faced blonde who claims to be Evelyn Smith answers the door. Confused, Johnny convinces a passing policeman to question the phony Evelyn, and the officer is introduced to a man calling himself Senator Remmy and another who claims to be Norton, the chauffeur. Convinced that Johnny is a "psycho-neurotic" veteran, the policeman accepts the impostors and leaves Johnny on the highway. At that moment, Blackton, who has never met Remmy, arrives at the senator's. A few minutes later, Johnny, still dressed in his bathing suit, sneaks into Remmy's house and steals some dungarees, unaware that the real Norton is tied up in a nearby closet. As Bazooka barks and draws the attention of the three spies, who are rifling through Blackton's clothes in the library, Johnny sneaks in and steals Blackton's leather jacket, in which he had placed his list of Nazi criminals. After Norton frees himself and is pursued by the spies, Johnny stumbles on Blackton's naked corpse, then hears Evelyn, who is also tied up, pounding on the floor above. Johnny unties Evelyn and they flee, leaving an unconscious Remmy behind. Later, the police question the revived Remmy about Blackton, and Norton tells them about Johnny stealing his pants. As a manhunt for Johnny and Evelyn begins, Johnny's car has a flat tire, and the couple is forced to stop at a motel run by Captain Caleb Simpson. Johnny and Evelyn, who is wearing a bathrobe and slippers, pose as recently eloped newlyweds and are given a cabin by the trusting old captain. Also at the motel are the spies, who are still searching through Blackton's clothes for the list. When the police interrogate Simpson about Johnny and Evelyn, he lies on their behalf, then gets them to confide their plight. The next morning, Johnny and Evelyn and the spies conclude at the same time that Norton must be involved in the operation and return separately to Remmy's house to find him. Sure that Norton is a Nazi, Johnny beats him up and is about to extract a confession from him when he is shot through a window by one of the spies. Johnny and Evelyn elude a police barricade by driving with Simpson on the beach and crashing into the surf. While stopped at the barricade, the spies learn that Johnny has Blackton's jacket and deduce that the dog they saw at the motel must belong to him. The spies return to the motel just as Johnny and Evelyn are writing a letter to Remmy in which they describe their enemies in detail. After the spies find Blackton's coat in Johnny's car, they force the couple into their car. While the spies are driving to a dock, where they plan to set the couple adrift in a leaky boat, Johnny, who is trapped in the trunk, sends a Marine SOS using the car's taillights. The signal is read by some sailors, who alert the police. As Johnny then fights with the spies at the dock, the police, who have been given Johnny's letter by Simpson, arrive in a speedboat. Cleared of all suspicion, Johnny and Evelyn marry.