Colton Barnes, Royce O'Connell, and Charlie Porter return to face a new threat to the United States as the possibility of a second civil war hangs in the balance.

In an alternate history of the United States where the Civil War lasted 10 years, a brilliant scientist is kidnapped by a crazed madman known as John Conway, the United States Marshals are called upon to prevent the impending disaster. To track down Conway, Marshal Colton Barnes enlists the help of Sheriff Royce O'Connell, who has been living in seclusion in an attempt to forget his painful past. Together, they set out with a team of Marshals to hunt down Conway. But nothing can prepare O'Connell or the Marshals for what awaits them.

One year has passed since the Rebel Uprising and the death of Jeremiah McKinley; Royce O'Connell is on the trail to rescue his friend Eli and bring down the Company, an organization that caused the death of Colton Barnes. Charlie Porter is back, alive and well, and on a mission to find Royce and bring him in, as she blames him for the death of Colton. With her on her mission is young deputy marshal Stephen Cooper, who is eager to show that he is no greenhorn. As Royce tracks down members of the company, he encounters a young, adventurous girl named Victoria, as well as bounty hunter Lee Conners, a man from Royce's past who's loyalty is only to himself.