It's 1871. 12-year-old Billy McCarty and his immigrant Irish family have to leave New York and travel west to seek new opportunities. But the journey proves fatal for some.

Kathleen and her sons Billy and Joe travel on to Santa Fe. Life is hard, but she meets and marries a man who might change everything for the better - only to find that he makes it a lot worse.

Antrim, Kathleen and the two boys relocate to Silver City, trying to start a new life, but all their dreams are shattered - and Billy loses everything.

Billy finds fresh trouble when he falls in with a character called Alias. Hehugs a man in self-defense and ends up on the run, and then in the arms of a young woman - who also happens to be the girlfriend of Jesse Evans.

Billy, on the move again, ends up in Chihuahua, Mexico, with a new Mexican friend called Segura. Together they enjoy several risky escapades - but in the end, Billy risks losing his life.

Billy bumps into a new character called Pat Garrett, who is riding with Jesse and the 7 Rivers Gang. Billy joins them - but law makers are already closing in. They plan to flee to Lincoln County - but not before Billy fulfils one last promise.

Billy rides into Lincoln County to join up with the gang, who are working for Lincoln's most powerful boss, Major Murphy. Murphy wants them to get rid of his new competitor, John Tunstall. Billy finds himself torn between the two rivals.

On the eve of the Lincoln County War, Jesse and the gang are encouraged by Murphy to ramp up their attacks on those famers, mostly Mexican, who have signed up with Tunstall; it's the last straw for Billy, and he decides to change sides.