TWO IMAGES dominate this novel of 17th-century Jesuits in Canada. The first appears near the beginning when Father Paul Laforgue, awaiting an audience with Samuel de Champlain in the fort overlooking Quebec, glances up at the commandant's quarters. There, framed by a window -- motionless as an oil portrait -- he observes the face of Champlain. That face symbolizes the power of royal France, with whose endorsement these priests undertook their dangerous, obsessive, often futile journeys of salvation into a wilderness populated by uncomprehending aborigines.

The second picture gradually materializes at the end of Laforgue's journey and is as chaotic as Champlain's face is static. We are presented with a scene of tortured faith, disintegration, murder, disease, uncertainty, and the implicit lowering of a curtain. Through it all Father Laforgue asks questions of himself and of his God, questions to which there can be no ultimate answer.

Brian Moore, the experienced Canadian novelist of Irish birth (The Lonely Passion of Judith Hearne and, most recently, Cold Heaven) explains in a preliminary note that by way of Graham Greene's essays he was led to Francis Parkman's history of the Jesuits in North America, and from that book to the original source: a collection of letters, the Relations, sent by New World missionaries to their superiors in France. And from the works of latter-day anthropologists and historians, who have established many facts unknown to those Blackrobes, "I was made doubly aware of the strange and gripping tragedy that occurred when the Indian belief in a world of night and in the power of dreams clashed with the Jesuits' preachments of Christianity and a paradise after death."

The most startling facet of Black Robe is the insistent use of scatological expressions by les sauvages. Moore notes that this was a form of rough banter, not meant to be offensive. And after some pages, in accordance with a law of human behavior, these pungent maledictions do seem less disagreeable.

Thus, accompanied by a young carpenter named Daniel and a torrent of abuse such as one does not employ in the presence of one's mother, Laforgue embarks on a canoe trip to the Ihonatiria mission in Huron territory. He will replace Father Jerome, who is ill, or succeed him if he has been murdered. He may have been murdered because the region is plagued with sickness and these superstitious Hurons hold the Blackrobes responsible.

Several Algonkian families en route to a winter hunting ground have agreed to guide the Frenchmen as far as the Great Rapids -- though without enthusiasm because they will be entering Iroquois territory. These Iroquois not only are fierce and numerous, but sometimes eat captured enemies. The voyage is further complicated by a tender morsel named Annuka who has been exercising herself with young Daniel whenever they get the chance.

Well, the perfidious Algonkian decide they have not been paid enough; all at once they turn around and paddle swiftly out of sight. Daniel becomes distraught at the prospect of losing fair Annuka and paddles desperately after them, leaving Father Laforgue on the riverbank.

What to do? Laforgue resolves to continue alone, but night is falling so he curls up at the base of a tree. Presently he is wakened by guttural voices. Iroquois.

THE IROQUOIS are still around when Annuka's father, troubled by conscience, returns with his family to help the Blackrobe. This was unwise. "Laforgue saw Chomina turn to his wife as she fell, blood spurting from the arrow wound in her throat, saw Daniel on his knees, trying to protect his head and neck as the Savages with wild shrieks . . ."

Chomina's wife dies, but the others -- Laforgue included -- are tied up and led to an Iroquois village where they are kicked, bludgeoned, and toasted with firebrands. Daniel gets a javelin through the palm of one hand. Laforgue has an index finger sliced off with a sharpened clam shell. Annuka's kid brother is chopped to bits and tossed into a kettle.

Before dawn, in one of the most bizarre scenes on record, they kill their sleepy guard and escape. How two maimed Frenchmen, a girl, and her battered father could then elude a flotilla of exasperated Iroquois warriors seems miraculous, but in novels and movies such things happen.

Annuka's father begins to spit blood. "Already, he had assumed the pose of those who live in the world of night, squatting, his head down, his arms folded across his chest." They leave him to die and continue toward the mission until the girl abruptly balks, for it has been prophesied that Laforgue must enter the Huron village alone. She and Daniel will proceed on foot.

So, doing his best with a mutilated hand, Father Laforgue paddles on toward Ihonatiria.

He finds one priest nearly dead of a crippling stroke; the other has been killed by Hurons who regard Blackrobes as sorcerers. Literally and figuratively this must be the end. All he has left is faith. But what's the good of it? "He looked up at the sky. Soon, winter snows would cover this vast empty land. Here, among these Savages, he would spend his life."

In Father LaForgue, bewildered by a hideous cultural collision, Moore embodies those valiant and now almost forgotten Jesuits who plunged into the wilderness three centuries ago with little to sustain them except a conviction that come what might, they would do their best.