Billy Blue Cannon faces possible hanging when he is court-martialed on the charge of killing an army general's son.

Billy Blue saves an Indian girl from advances by a drunken army lieutenant, who is killed in the fight. When the girl flees to the Apache stronghold, Buck and Manolito risk their lives to persuade Cochise to release Blue's only eyewitness. Her testimony is discarded when the court learns her release was obtained by a bribe. It becomes obvious to John Cannon that the court-appointed defense is incapable of saving Billy Blue, and John personally takes over his son's defense

Billy Blue Cannon quits the ranch after a quarrel with his father and leads a peace representative of the President to Cochise.

On the trail Blue falls in love with Kelly's adopted Apache daughter, Moonfire. Kelly, an idealistic dreamer, meets Cochise's demands for a strip of land separating the High Chaparral from Tucson. This would cut the Cannons' supply route and threaten them with bankruptcy. John, angered by the peace terms and his son's choice of a wife, prepares to defend the ranch against the Apaches.