In the fall of 1868, eighteen-year-old Aaron LaCroix leaves his family homestead on the Mississippi bound for adventure. At his Army post in the far northwest of Indian Territory as a part of the Seventh Cavalry, he makes the acquaintance of Reid McKinstry, a lanky teenage Texan whose outgoing personality provides a foil for LaCroix's taciturn one.

Over the course of their journeys, LaCroix and McKinstry encounter renegades and pursue wanted men; they drive cattle and work as bounty hunters. Eventually they are sent on a special mission that culminates with a heroic act for which they will always be remembered, and come into contact with someone they did not expect from LaCroix's past.