During World War II, after completing a twenty-one day vitamin sustenance experiment at the Pacific Coast Guard naval experiment station, Coast Guard seaman Howard "Howie" Young returns to his former duties as a radio announcer. While eagerly awaiting his orders to ship out and fight the enemy, Howie meets and falls in love with singer Christine Bradley. Believing that Howie survived twenty-one days at sea, adrift in a raft, Christine considers him a hero and consents to go on a date with him. Christine does not know, however, that Howie was never at sea and that he spent the entire time in a simulated raft at the experiment station. Afraid that he will lose Christine if she discovers the truth about the experiment, Howie plays the role of the hero for her. Christine soon discovers his ruse when she checks Howie's personnel file and upbraids him for lying to her. Howie later apologizes to Christine, and all is forgiven. Soon after Howie gets his orders to ship out, his joy turns to disappointment when he realizes that he is being reassigned to Catalina Island, only a short distance off the coast of California. Howie allows Christine to believe that he will be far away, but realizes that he cannot write to her, as his return address will reveal his true location. Time passes, and Christine, concerned that she has not received a single letter from Howie, asks his friend, Chuck Enders, if he has heard from him. Chuck tells Christine that he has not been in contact with Howie, but he tries to ease her pain by giving her a song recording that Howie made before he left. When Christine plays the recording during a rehearsal of Lieutenant Scully's "Tars and Spars" show at the Coast Guard recreation hall, Scully hears the beautiful singing voice and decides that he must have the singer perform in his show. Christine tells Scully that the voice is Howie's, and Howie immediately receives orders to return to the mainland. Back at the Coast Guard base, Howie confesses to Christine that he was on Catalina Island, and she is again furious with him. Christine calls Howie a coward for making her suffer to protect his pride, but they eventually reconcile and begin rehearsals for the show. Howie soon finds himself on a ship bound for the combat zone, however, and following a series of misadventures, meets up with the "Tars and Spars" troupe in time to appear in the show's opening. Meanwhile, in her dressing room, Christine plays Howie's recording, dreaming of the day that "she will be reunited with him." After turning off her record player, Christine is surprised to hear the song continue, and is happy to discover that Howie is singing the song in her dressing room.