On the eve of the 1860 presidential election, and in front of a courthouse of American justice, Jacob Israel Christmas stands for sale at the third slave auction of his life. At thirteen, he has been separated from his mother for three years, has run away, and then been captured, all the while wondering, "When will I be free?" If Abraham Lincoln is elected, Jacob knows there's a chance for freedom; if not, slavery could spread west, all the way to California.

When a rich, young prospector named Honorable Mister Clarence Higgenboom buys ten slaves -- reuniting Jacob with his mother and friends -- Jacob can't believe his luck. But when Jacob suspects the Honorable Mister of being a dishonorable murderer and thief, who plans to rob a stagecoach carrying Pony Express wages, Jacob knows he must stop him! Without wages, the Pony Express will refuse to ride...and they've got the important job of carrying the election results to California.

As the master, his pregnant wife, and his ten slaves set out on a two-thousand-mile trip from Missouri to California, a harsh winter descends on the country. Despite the cold, Jacob never loses sight of his purpose: to make sure that the Pony Express rides...no matter what.