Someone's stealing gold shipments in Colorado. John Whyte, ace Pinkerton detective, is tasked to find the culprits and bring them to justice. He is joined by his friends and associates: Khan Singh, his loyal Sikh manservant from his service for the Queen in India, who followed him to America and fought at his side in the Civil War; and Curly Bill Williams, his American friend from Texas. John investigates the string of brutal robberies of gold shipments from the mines in central Colorado en route to Denver, where the precious metal is refined into gold coins at the US Mint. John enlists the aid of a lovely Irish madam, who impresses him with her sharp mind as well as her physical charms. Together, they solve the mystery, and in a series of shootouts break up and destroy the gang, including the arrest of its surprising leader.