Raised in poverty in Missouri, Mac is determined to find a better life for himself and the girl who is still a vague vision in his mind. Work on the Santa Fe Trail, and on a Mississippi River boat give him a start, but the years of Civil War leave him broke and footloose in South Texas. There he discovers more cattle running loose than he ever knew existed. Teaming up with two ex-Federal soldiers, he sets out to gather his wealth, one head at a time.

While gathering and driving Longhorns, Mac and his friends meet an interesting collection of characters, including Margo. Mac and Margo and the crew learn about Longhorns, and life, from hard experience before they eventually head west. Outlaws and harrowing river crossings are just two of the challenges they face along their way.