El Puma, a Mexican desert guide, escorts an archaeological expedition headed by Professor Lucius Lloyd through the Indian badlands of Mexico. Marian, the professor's niece accompanies the party as only she can translate the Aztec writings in the diary of her father, murdered on a similar expedition six years previous. The professor is murdered by a knife, and the weapon is recognized as the property of El Puma. Magpie, a Federal Investigator, knows that El Puma is really "Lightnin' Bill' Carson, a former federal agent who has been missing since Marian's father was slain. The reluctant Magpie believes that his old pal is guilty. Carson sets out to prove otherwise.

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.

When Len Stoddard wins Ted Ames ranch in a poker game he sends his brother Jake along with Ted to take over the ranch. When Jake is found murdered he offers a reward for the capture of Ted who now is believed to be a member of the Black Aces gang. Ted finds the probable location of the gang's hideout and sets out to clear himself.