In 1858, four hard men ride across the border into the New Mexico Territory. Their target is a large ranch where they hope to get rich. After the raid they ride off with a box of ancient coins, leaving the rancher's family dead and the ranch burnt down. Before he dies the rancher sends a letter to his friend, Abraham Lincoln.

During the Civil War, some of the stolen coins turn up in the western Territories. President Lincoln nominates former Cavalry Captain Joseph "Joe" Pernell as U.S. Marshal and requests him to follow the trail of coins and get justice for his dead friend.

From Fort Union in New Mexico, the Marshal starts his search which ultimately brings him to the Montana Territory, where he was born and raised.

During the journey Joseph Pernell has to use his wits and military experience more than once to solve the mystery of the stolen coins and to bring the raiders to justice.