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.

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.