John Cannon risks breaking a mutual defense agreement with Victoria's father and dissolution of his marriage when his ranch hands join a posse searching for marauding bandits in Mexico.

Marshal Virgil Shanks leads the posse into Mexico and comes into strong conflict with Buck and the Cannon cowhands when he disregards the delicacy of the situation and rides boldly onto Montoya land. Manolito finds the bandit leader, El Lobo, on his father's land and attempts to move the bandits out before the posse moves in for the kill.