After being paid off for delivering horses to the army, Del Gannon and his partner, Johnny Concho, stop off in Yuma. Del aims to quit the tough business of bronc busting and buy an orange farm in California. Johnny holds the money while Del gets cleaned up in readiness for signing the contract, but Johnny is robbed and killed. Bent on revenge, Del finds the killers and rescues a young Indian, Lone Wolf, from their clutches, but one of the killers escapes. Lone Wolf, the son of Yuma Indian chief, Painted Tail, presents Del with some mysterious black stones. The part these stones play in bringing Johnny's killer to justice makes for a breath-taking scenario in a tale of duplicity and courage.