A Jesuit missionary living among the American Indians in the 1840's is declared a traitor and an apostate for committing the unpardonable offense of siding with the tribes. Fr. Stephen Morgan is caught between the tribespeople he has come to love and the expanding American nation. The story begins as Stephen lies gravely wounded, after a Dakota village is attacked by the US cavalry. He's found by White Fawn, who has grown to love and respect the blackrobe, and who tries to prevent his capture by the soldiers who are searching for him. Captain Gatewood hates his new assignment, which has taken him from his wife and family back east. Because he inadvertently says that he once knew the renegade priest, he is reassigned by the army to Indian country to hunt him down. We follow Stephen through his early years when he meets Andrew Jackson, who is running for the presidency. He hears the doctrine of manifest destiny, the notion that the American nation was divinely ordained to take the land from the tribes. He witnesses the 'trail of tears'. Stephen's formation as a Jesuit is recounted, during which he witnesses the devastation of the Mandan tribe from smallpox. It is here that he first meets White Fawn, the chief's granddaughter, as they minister to the victims of the epidemic. Meanwhile Red Thunder, a Lakota chief, recognizes the urgency of preparing for the advancing white men, who have destroyed the eastern tribes and taken away their lands. Believing it is a question of communication, he sends his twin sons to be educated by the blackrobes in the white man's ways. Lone Eagle and Fire Hawk arrive in St. Louis where they meet the blackrobe Stephen, whom one befriends and the other distrusts. Both braves soon run away from the boarding school and return to their tribe. When Stephen is ordained, he heads west with the famous missionary, Fr. Peter DeSmet. Their wagon train is attacked by Dakota warriors among whom are Lone Eagle and Fire Hawk. Stephen negotiates to live among their people for the others in the wagon train to pass through. He again meets White Fawn, whom he thought had died during the smallpox epidemic. She helps him learn Dakota ways and to integrate into the tribe, which he must do before being allowed to preach. His mentor is Vine, an old medicine man, who is the keeper of the Dakotas' sacred pipe. The priest and the medicine man exchange compatible views. Stephen keeps a diary which traces his spiritual odyssey, the challenges he faces and his own doubts. He finds that he learns as much as he teaches, and receives as much as he gives. The reader accompanies him as he travels with the tribespeople and observes the beauty of their lands. He witnesses buffalo hunts, shamanic healings, and battles of enemy warparties. He participates in ceremonies and rituals, and gradually earns the tribespeople's trust. When Colonel Kearny and a regiment of dragoons arrives with the intention of building forts in their country, the chiefs rely upon the blackrobe to warn him of impending war. Stephen tries to intercede and runs afoul of the colonel. A commission is sent from Washington to negotiate a peace treaty, which almost succeeds. But when Stephen translates for the chiefs what the treaty actually states, as opposed to what they have heard from the commissioners, the negotiations break off and Colonel Kearny accuses the priest of treasonous interference. Captain Gatewood has only three days to find the renegade blackrobe. If he fails, Kearny will accuse him of aiding and abetting his friend. When his religious superiors are told that he is siding with savages, Stephen is accused of apostasy. BLACK ROBE details the odyssey of an idealistic priest who came to defend the way of life of the tribespeople. It narrates the story of the nation's westward movement through the eyes of a missionary living among the tribes.