Texas hill country, 1868. Nineteen-year-old Benjamin Shreve witnesses a stagecoach strand a passenger. When the man, a treasure hunter, persuades Benjamin to help track down the coach, they discover that its passengers include Nell, a pregnant woman, and her four-year-old son, Tot, who are fleeing Nell's husband and his murderous brothers. Benjamin offers to deliver Nell and Tot to a distant port on the Gulf of Mexico, where they can board a ship to safety. He is joined by two other companions: the treasure hunter whose stranding began this endeavor and a Black Seminole who is a veteran of wars on both sides of the Rio Grande and who has an escape plan of his own.