If the man of the mountains, Tate Saint, had a fault, it was that he had a hard time saying no whenever someone needed his help. But now he has a family and the wilderness makes many demands on anyone that tries to master the mountains. And if a redheaded Irish wife, a curious toddler for a son, a wolf for a hunting companion and a bear cub for a playmate for his son wasn't enough, a legendary mountain man, Old Bill Williams, recruits him to help John C. Fremont on his expedition to find a route through the Sangre de Cristo and San Juan mountains in the middle of winter. When the elder statesman of the mountains, Williams, tells Fremont it can't be done, the Pathfinder expects Tate Saint to get them through.

But this venture soon becomes one of the most treacherous and deadly expeditions of the times. Facing the full onslaught of a Rocky Mountain winter with twenty-foot snowdrifts, below zero temperatures, and every other hazard that could be brought to bear, the challenges must be met and conquered. But the things that must be done and the sacrifices that must be made become more than anyone expected or wants to remember. One of the greatest challenges of the young mountain man's life must be met and conquered, or he and many others will die.