Bent on unearthing the two Union traitors who sold gold shipment information to Confederates 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 friends, the McNally and the Confederate captain Pierre Cordona ride into Rio Lobo--a dusty town in the middle of the desert overcome by corruption--to bring to justice the remaining traitor who sold McNally out; however, the town is rife with the betrayer's murderous cut-throats. Can McNally avenge his bosom buddy and clean up Rio Lobo?