With the end of the beaver trade at hand, free trappers like Titus Bass must somehow make their way on a changing frontier. Drawn by the promise of adventure and wealth, Bass joins an expedition to Spanish California, where the ranchos have horses and mules in abundance. Their plan is to steal the livestock and drive it back east across the great Mojave Desert to sell to fur traders for top dollar. But pursuit by formidable Mexican soldiers and an attack by fierce Digger Indians take their toll on Bass and his fellow raiders.

Arriving back in the Rockies, the mountain man discovers that even the famous Jim Bridger has abandoned trapping and settled down to trade with overland immigrants plying the Oregon Trail. Wondering where his own trail will lead him, Bass journeys south for a reunion with an old friend in Taos-only to be caught up in the "Taos Rebellion." And in its tragic aftermath, Titus finds himself once again an outsider in a world he no longer recognizes.