During World War II, Merchant Marine Toby Smith tells his shipmates the true story of what happened to him the previous summer: While sailing out from Australia, Toby's ship is torpedoed and he, bosun Pete Jenkins, and radio officer Ken Masters are marooned on a nearby island. After thirteen days, a Japanese plane lands on the island and the three Merchant Marines capture the Japanese and steal their plane. They are shot down, however, by an American battleship and are stranded on another island. The second island is occupied, however, and Dr. Curtis, an American physician who had been shipwrecked there years earlier with his daughter Lona, advises the queen of the islanders, Queen Okalana, that the plane is evil as it comes from the land of the "Rising Sun." When Toby, Pete and Ken revive from the crash, they are surrounded by beautiful English-speaking island women. Queen Okalana deems that Toby, Pete and Ken should be executed but Toby squirms so much that the executioner is unable to chop his head off, and Lona suddenly sees a resemblance between Toby and a carving of their sacred god, Momo. The execution is halted, and Toby is hailed as a god. He then saves Pete and Ken by dubbing Pete, "Twerpo," his slave, and Ken, "Gogo," the master mechanic of the "iron bird." Lona falls in love with Ken and threatens to reveal Toby's true identity to her people unless Ken agrees to let her leave the island with them. Lona performs a dance during which she places a flower lei on Ken and tells him to respond with a kiss. Lona's jealous fiancé Alcoa picks a fight with Ken, but when Ken strikes him, his ring leaves an imprint on Alcoa's chin, and Dr. Curtis claims it is the mark of "Momo" so that the islanders will back off. Alcoa and high priest Kahuna are determined to prove that Toby is not a true god, as any man who pretends to be a god will be executed by a man-eating plant. Each time Toby comes close to revealing his human foibles, such as eating, he is saved by sheer luck, or Pete's ingenuity. Dr. Curtis advises a lovesick Lona to proceed with her marriage to Alcoa in order to make Ken jealous. When Queen Okalana is shown a set of spark plugs from the plane, she becomes suspicious that a god needs machinery in order to fly, and wears the plugs as a necklace. During Lona's premarital rite of purification, Ken realizes that he has fallen in love with her, and that night, he romances her and urges her to get the necklace from the Queen while she sleeps. Lona is about to carry out her mission when she is caught by Alcoa, who insists on placing her under protective guard. Ken then reluctantly romances Moana to induce her to steal the necklace, but Lona overhears his overtures and ruins Ken's plans. Toby then dresses up as a island woman and convinces the Queen's guards that she has sent for him. Pete, meanwhile, digs a tunnel under the fence around the queen's compound as an escape route. Unfortunately, he comes up between Kahuna and the guard Akana. By this time, Toby has administered a sleeping potion to the queen and the islanders believe she has died. Alcoa gives Toby until sunrise to prove that he is a god and revive the queen. He fails, and the next morning, he is tied up on a funeral pyre to burn alongside the queen. Curtis convinces Lona that Ken's intentions toward her were honest, and that he only used Moana to help free them all. Curtis cuts the ropes around Toby's hands as the pyre is lighted, while Toby grabs the spark plugs. The islanders are astonished when the queen finally awakens, and the three Merchant Marines, plus Curtis and Lona, run for the plane. To give Ken time to start the plane, Toby and Pete allow themselves to be chased by the islanders. Ken and Alcoa fight until Lona knocks Alcoa out with a monkey wrench, after which the plane takes off with the sailors. Toby concludes his tale by noting that they were picked up by an American cruiser. As proof of his story, Toby offers a photograph of Lona, but the sailors recognize her as actress Dorothy Lamour, and Toby affirms that this is how she got into the movies.