Mexican-bandit Montero and his deaf-mute sidekick Coloso are being pursued through the sand-dunes of southern Arizona by lawman Bob-Cat Manners and his posse. Montero has intentions of robbing the bank owned by skinflint Lucius Perkins, but is sidetracked by the attractions of singing-teacher Helen Wardell. He learns that Perkins has marital designs on Helen and holds the mortgage on her ranch. But Helen is in love with Bill Howard. Perkins offers Montero money to kill his rival.