When the government’s star witness against Mike Bigelow, Mary Marvin, telephones Detective Speed, it is too late. Bigelow’s henchmen, Slick and Hunch, sneak up behind her while she’s on the phone. Richy the Amazing Boy, Trigger Quick, and Rang-a-Tang listen on the other end of the line while Mary is murdered by the mobsters.
When Hy Speed returns to town with Linda Lane, they notice a resemblance between Linda and the murdered Mary. Concocting a scheme, Linda pretends to be Mary while boarding a train with Detective Speed. Rang-a-Tang is in a piece of luggage while Trigger Quick and Richy take up disguises. They soon capture the thugs.