Romantic adventure film in which the girl Betty, who dreams about pirates, and her gullible father is tricked by a set of real pirates. They are rescued by a young man who has a crush on Betty.

Mildred Manning, known as Middy, is an apprentice in Madame Lizette's fashionable shop. Her beauty is discovered by Madame's brother, George Martin, and she is made a model. One afternoon, she tries on a rejected bathing suit and by adding a touch here and there, makes it into a beautiful creation. Madame then sends her to the beach to carry out a clever advertising scheme. At the shore, Middy is pursued by a reporter and photographer, who have been commissioned by Madame to photograph the girl for calendar advertising. In her flight from the publicity men, Mildred takes refuge in a car owned by lawyer Philip Gordon, who gets into the vehicle and drives off with Middy. Middy has him drop her off where she doesn't live, and he ends up having to try to track her down.

Mary Beth rents an attic room to Richard, a composer. Frustrated with the publishers demands for cheap, trashy songs, Richard, penniless, tries to asphyxiate himself, but Mary intervenes, encouraging him to go on. Mary finds his song, and secretly sells a song she finds of his, "The Rainbow Girl", to a publisher, later finding out that she, herself, is the Rainbow Girl he wrote about.

Retired gem merchant Peter J. Martin hires detective Dan McRae to guard a large diamond which he plans to present to his daughter Ruth on her twenty-first birthday. Notorious jewel thief Gentleman Joe overpowers McRae, however, and takes his place at Ruth's party.