Filmed in Mexico and released through Eagle-Lion Classics, the picture is based on the book South of the Rio Grande by Max Brand and is sometimes referred to as My Brother, the Outlaw.

In the town of Border City, Texas, a bandit known as "El Tigre" blows up and robs a bank.

El Tigre is a dangerous killer with a large gang wanted on both sides of the border.

The Mexican Secret Service who have attempted to infiltrate El Tigre's gang have had all of their operatives killed or disappeared.

The Mexicans assume that if a Ranger approaches O'Moore and gets him back to America he would be willing to betray El Tigre for money and amnesty.