Rough-and-tumble federal agent John Wyatt (John Wayne) receives an unusual undercover assignment: He must infiltrate the ranks of an Arizona-based medicine show. Wyatt's boss suspects the show's shifty-eyed proprietor, ex-convict Dr. Carter (Earle Hodgins), of running a massive counterfeiting operation. With the full cooperation of the local authorities, Wyatt poses as a sharpshooter and begins his investigation -- only to fall for Carter's beautiful daughter, Linda (Marion Burns)