Ballard's trail jumpers attack the Wyatt Company wagon train, killing young John's parents and kidnaping his brother, Jim. In post-Civil War California, John Wyatt, now a man, pulls together a vigilante posse, The Singing Riders, who all ride white horses, dress alike, and ride the trails singing and rounding up outlaw gangs. Meanwhile, John is ever on the lookout for the gang that murdered his parents.
In the late 1840's, as Mark and Hannah, "Ma" Wyatt and their young sons John and Jim drive cattle across the California desert, they are attacked by Walt Ballard's gang. Jim is forced to join the gang as the family's wagons are burned. John falls off the wagon during the battle, but survives and years later forms a vigilante group to help fight the many groups of lawless men who wander the territory. When the Black Bart gang attacks a town, the vigilantes capture them. John learns that the Gordon herd is being driven through his area, and joins Lafe Gordon as trail guide without revealing his true identity. John and Lafe's daughter Mary yell at each other, but nonetheless she likes him. Ballard sends Jim, who is also grown but does not know the gang killed his parents, to spy on Lafe. Jim stumbles toward John and the Gordons and pretends to have been robbed. John is suspicious, and later Jim convinces Lafe that John is a fraud. The next day, finding Jim gone, John searches for him. Meanwhile, Jim returns to Lafe and convinces Lafe to proceed into Ballard's trap that evening. John and the vigilantes spoil Ballard's plan and save Mary's runaway wagon. Ballard and his men regroup, and John begins a search for the gang. Jim tricks Mary into being taken prisoner while John gathers the vigilantes. Mary overhears Ballard's head henchman, Red, mention that John and Jim are brothers. John receives a note that instructs him to ride to Blind Canyon to save Mary. While Ballard and his men rob the bank, Jim realizes he has been abandoned by his confederates, and releases Mary and learns the truth about John. Jim saves John from an ambush and explains what Mary has told him. Mary summons the vigilantes as John and Jim begin an attack on Ballard, who is killed as his wagon goes over a cliff. Jim, however, is also killed in the battle, and Mary agrees to return to California with John.
