After the conclusion of the American War of Secession, while Confederate prisoners remain in the hands of the Unionists, some die-hard Southerners refuse to accept General Robert Edward Lee's surrender and join outlaw bands to continue their fight. One of these men is captured and sentenced to death, but is granted a pardon when it is discovered that he is privy to extremely secret information, information that only a few senior Northern officers were allowed to know. The man does not know how his boss obtained this information, but it emerges from his account that the 800 or so men in the gang were deceived: Fort Yuma and its treasure are no easy prey, and an assault on the fort would only lead to needless slaughter. To avoid an unnecessary massacre, an officer instructs two NCOs to deliver a message to the commander of Fort Yuma to inform him of the situation. Meanwhile, another cunning ex-confederate named Gary Hammond is freed with the assignment to investigate and find out who the mole is who provided such secret information.