In 1820, Capt. Filmore Henry leads an expedition of trappers through the unexplored Northwest territories. With an unwieldy amphibious boat, filled with furs and dragged by mules, the few dozen men struggle to reach the Missouri River before winter so they can sail south and trade their goods. One day, young trapper Lowerie kills a deer in the brush. Despite the animal’s precarious location, scout Zachary Bass is obliged to retrieve it, and in doing so is viciously attacked by a bear. As Zach is mauled, Lowerie, too scared to shoot, runs for the rest of the men, who manage finally to kill the bear. Upon examining Zach, they are dismayed to discover that he is severely wounded. Henry orders the party’s doctor, Ferris, to sew up Zach’s wounds, but soon announces that the expedition must go on. Sure Zach could not survive the trip, Henry orders two men to stay behind with Zach and bury him when he dies. With no other volunteers, Lowerie and Fogarty, a grizzled hunter who hopes to have Zach’s gun, finally agree to stay. Before leaving, Henry tells Fogarty to kill Zach if he is not dead by morning, then instructs Lowerie to say a short eulogy over the body. Unaware that Zach is conscious and listening, Henry intones, “He fought against life all his life; now his fight’s against you, God.” Delirious, Zach recalls being orphaned as a young boy, then revives in time to see the party leaving. As they move forward, the other scout, an Indian, stops to say a prayer over Zach and drape an amulet around his neck. That night, after digging Zach’s grave, Fogarty scares Lowerie with tales of Indians, annoyed that Zach continues to hang on to life. In the morning, Fogarty and Lowerie spot some Arikara Indians nearby, and eager to run, Fogarty aims his pistol at Zach. When Zach attempts to speak, Lowerie stops Fogarty from shooting, but after apologizing to Zach, flees with Fogarty, leaving behind his Bible. Seeing it, Zach remembers being abused by an orphanage priest for refusing to agree that God created the world. The Indians pass by without incident, but later draw Henry’s vehicle on a teepee wall. Soon after, a wild wolf approaches Zach, who finds the strength to roll out of the way. Landing near the riverbed, he struggles to bring water to his mouth. When the Indians return, Zach hurls himself into the grave to hide. Although the chief finds him, upon spotting the amulet, he says a brief prayer and leaves him. Feverish and near death, Zach drifts in and out of consciousness. He remembers his pregnant wife, Grace, urging him to believe that God is in him and all things, but he insists that he has never felt God’s presence. She puts his hand on her belly to feel the baby kick, after which he whispers to his unborn child that although he will not be there for the birth, and despite his belief that life is hell, he loves his wife and child. In the present, Zach, still unable to sit up, covers himself with leaves to protect against the rising wind. Meanwhile, Fogarty and Lowerie reach Henry’s boat and report that they left Zach alive. Declaring they cannot turn back, Henry tells his men that although Zach was like a son to him, he would be proud of Henry’s decision to go on with the endeavor to settle the wilderness. Later, Zach digs out, and with renewed but still limited energy, crawls to the water, grabs a crab and eats it, then spots berries and crawls to them. He then covers himself in mulch and once again recalls Grace. By morning, he spots two wolves nearby eating a still-live buffalo. Crawling to them, Zach beats the animals off with a stick, grabs a hunk of bloody flesh and crawls away to eat. Soon after, the trapping party, continuing over the now-snowy ground, spot the Arikara Indians and arm themselves. Although the chief raises his hand in peace, Henry orders the cannons fired. Once the Indians retreat, Henry alarms his men by ordering them to turn and shoot behind themselves, as well, for no discernible reason. As the Indian chief returns to his tribe and prays for guidance, Zach laboriously attempts to build himself a crutch. After breaking open an old bone to eat its marrow, he watches as nearby the Arikara kill a small party of trappers who have taken on Indian wives. Zach, who has been hiding, shakes off his horror in order to salvage knives, wire, a blanket and a razor from the carnage. By stropping the razor on the knife blade and using pages from his Bible as tinder, he is able to start a fire. After killing a rabbit, he uses the hide to form an armpit cushion for a crutch, then creates a small shelter and makes a poultice for his wrecked leg. Over the next few days, Zach recovers more fully. He fashions a spear out of the knife edge and a stick, then uses it to catch fish, vengefully picturing Henry’s face on his prey as he hurls the spear into it. Meanwhile, the trappers, reduced to eating sick mules, discuss Henry’s strange, paranoid behavior, and wonder if he expects Zach’s ghost to appear. Zach soon traps and kills a cougar, then cures and sews the hide to form a coat. Finally ready, he sets out to seek revenge against the men who left him to die. One day, as he is hiding from an Indian band out foraging, Zach witnesses an Indian woman give birth in the woods, alone and silent. This vision engenders the memory of Grace’s death during childbirth, an occurrence that further damaged his belief in God and prompted him to leave his son in the care of Grace’s mother. Soon after, Fogarty informs Henry that the men want to burn the boat in order to move on more quickly, but Henry refuses, stating that it is all that is left of his last command. When Fogarty asks why Henry seems unable to let go of Zach, the captain replies that Zach stole onboard his ship as a child, running away from the orphanage, and while Henry often thought of him as his son, Zach never allowed him to get close. Henry names Zach as the only man he ever respected or feared, and declares his certainty that Zach is alive. The next night, while Fogarty is on watch, he thinks he spots Zach in the woods and shoots him, only to discover that he has just killed Lowerie. In the morning they reach the river, but realize they are too late, as it has already frozen. Forced to continue on foot, they push the boat laboriously. Meanwhile, Zach finds a wounded rabbit and prepares a splint for its leg, then reads it passages from the Bible. As the days pass, his experiences living off the land and his memories awaken in him a more spiritual bent. One day, the Indians and Zach simultaneously catch up with Henry’s expedition. A gunfight erupts, and although Henry’s men have the cannon, the Indians outnumber them. Zach hobbles to help his comrades, and as he is fighting off several Arikara, the chief recognizes his amulet and orders his men to leave Zach alone. Approaching the bewildered Zach, the chief, who considers Zach blessed, returns his homemade spear to him and indicates that he should kill Henry. Zach approaches Henry, asking for the return of his gun. Although Henry fears he will be shot, Zach merely states, “I’ve got a son out there, and I’m going to find him.” As he walks off, Henry’s men leave their captain to follow Zach.