Los Angeles in the 1850s: John Dimas, a California Ranger, goes underground as a Franciscan monk. Dimas is hunting California's most notorious bandito, the feared Joaquin Murietta. During his perilous journey through the Sierra Nevadas, Dimas visits the daytime arenas where bear and bullfights entertain bloodthirsty audiences, the midnight faro games and fandango halls where knife and pistol rule. He meets Maura Walsh, a beautiful lady of means, and her fiance, Trenton Kerns, a man with dangerous hidden plans that place him squarely in Dimas' path.