The Girl in 313 is undercover police detective Joan Matthews (Florence Rice), who infiltrates a gang of jewel thieves. It is Joan's goal to unmask the leader of the gang, who is presently hiding behind a veneer of respectability. Piecing the clues together, she discovers that the crooks are in cahoots with a shady insurance company. Things look pretty bleak for Joan when her ruse is discovered, but she is rescued by Greg Dunn (Kent Taylor), the handsomest of the thieves, who has fallen in love with her. It took three writers to put together this 56-minute quickie.