The McCandles ranch is run over by a gang of cutthroats led by the evil John Fain. They kidnap little Jacob McCandles and hold him for a million dollar ransom. There is only one man who is brave enough and smart enough to bring him back and that man is Big Jake.

Bent on unearthing the cynical traitor who sold information to the enemy and caused the death of a dear brother-in-arms, the battle-tested former Union cavalry officer, Colonel Cord McNally, teams up with a pair of ex-Confederates after the Civil War. Now, as honest friends, the three companions ride into Rio Lobo--a dusty town in the middle of the desert overcome by corruption--to bring to justice the one who sold McNally out; however, the town is rife with the betrayer's murderous cut-throats....