Set in the early 1850s, this is a gripping Santa Fe Trail story for young readers. Peter Blair is a twelve-year-old St. Louis boy whose mother has recently died and whose father has gone to Santa Fe to seek his fortune. A St. Louis friend agrees to care for Peter. When his father's acquaintance "Uncle" Seth returns to St. Louis, he checks on Peter. The lonely boy persuades his "Uncle," a weather-beaten trapper, to take him to Santa Fe to be with his father.

Uncle Seth leads their wagon train through an Indian attack, desertion by greenhorns, a buffalo stampede, a violent storm, and other hardships. When Peter finally reaches his destination, he finds that his father has left Santa Fe. He must go on another journey, one that almost proves fatal.