The Morgan clan held rugged Dark Valley in an iron grip, was feared in two Southwest counties for their raucous drinks, their brutality and their ability to take whoever and whatever they wanted. Afterward they disappeared into Dark Valley, impenetrable, protected by mountains, iron gates, and armed guards.

The fellow they called "Crazy Barnaby" had a secret entrance and strange bond with Sid Morgan's fierce dog.

Texan Bolt Haveril finds a Morgan fugitive, saves him, then vows to save the man's captive sister and bring the cruel family to justice. Bolt also uncannily resembles a renegade Mexican called Don Diablo, who has been hired to bring young Morgan back.

That resemblance and a meeting with Crazy Barnaby are the keys to the Morgan Stronghold, if Bolt Haveril's complicated plan works....