 Ranger s Gene Autry (Gene Autry) and Frog Millhouse (Smiley Burnette) are on their way to solve the murder of old, half-blind Frank Martin and, when nearing town, they are forced off the road by a recklessly driven coach with Joan Martin (Barbara Pepper), the old man s granddaughter, at the reins. When he reaches town, Gene receives several high offers to sell a swayback horse in his possession, which, with a guitar string are the only clues to the killer of Martin. These offers come from liveryman Hank Polk (Fred Kelsey), Joan s sweetheart Lon Dillon (Dennis Moore as Denny Meadows), Henry Nolan (Hooper Atchley), the dead man s lawyer and from his foster-son John Martin (J. Frank Glendon) as all know the horse is the key to Martin s lost gold mine. Without letting anyone know who they are, Gene and Frog go to the Martin ranch to play for a dance, and the old swayback is placed in the barn with the intention of attracting the killer.