Amateur Crook: Jerry Cummings, a mining engineer, has pledged a large diamond on a short-term note to a pair of crooked loan sharks, Crone and Jan Jaffin, and heads for Mexico. His daughter Betsy, posing as a jewel thief called Mary Layton, is working to keep the crooks from absconding with the jewel, and her efforts are hindered greatly by an artist, Jimmy Baxter, who thinks she is a crook and Crone and Jaffin the good guys.