The Lawless Land — John Dyson

In the wilds of New Mexico territory, order has broken down completely. It is then that Nathan Strong rides into the abandoned Fort Sumner, now in the control of brutal outlaws, and makes three disastrous mistakes. Firstly, he kills one of Billy the Kid's friends, then falls for the Mexican beauty, Melody, for whom Billy has a passion. Finally, he joins a cattle-rustling expedition, which spells disaster for all.