On shore leave in San Pedro, U.S. sailor Jimmy Harrigan meets and falls for Sally Brent. She promises to wait for him when he ships out to San Francisco, but Jimmy becomes jealous and tells her off when he learns that she has entered a marathon dance contest sponsored by a lecherous snake named Baron Portola. Along with several of his Navy pals, Jimmy goes to the ballroom the night of the dance marathon to try to change Sally's mind and win her back.