Billy Parham and his younger brother Boyd are teenagers in Cloverdale, Arizona, in the early 1940s when a wolf, apparently having traveled up from Mexico, finds her way onto the Parham land and takes down several cows. Billy and his father, Will, begin to work a trap line, hoping to catch the wolf before losing any more cows to the wolf'shunger. The wolf finds the traps and exposes them to the light of day without springing them. Billy's father is disgusted with their efforts and Billy continues to work the line, often alone. He notes that the wolf digs one day in the abandoned campfire of a group of vaqueros, so Billy sets a -trap in a newly-abandoned site. When he returns the following day, the wolf is caught in Billy's trap. Billy now faces the dilemma of what to do with the animal he's trapped. He initially intends to go home and tell his father of the catch but can't bring himself to leave her behind, apparently fearful that she'll escape. Instead, he creates a makeshift muzzle and prepares to lead her home as one would lead a dog on a leash. When he comes to the crossroads - one direction toward his own home and one toward Mexico - he realizes that he feels the need to return her to her home rather than taking her to his.

Billy crosses the border and continues toward the mountains. He and the wolf come to an understanding of sorts so that she accepts it when he forces her on her side and dribbles water into her mouth and feeds her bits of rabbit liver and heart. Then Billy is confronted by some officials who take the wolf from him. Billy is helpless as the animal is pitted against many dogs. When the wolf, beaten and bloody, is shot, Billy trades his rifle for the animal's body and takes her on to the mountains to be buried.

Billy returns home to find that his house is deserted and learns that his parents were murdered. Boyd is being kept by a family and he and Billy, with almost no conversation, pack up and head into Mexico in search of the horses taken from their farm because they believe the horses will lead them to the murderers.

The boys have many near misses and then rescue a girl from bandits. Boyd is shot by some men associated with the horses taken from the Parham farm and when he recovers, Billy wakes one morning to find that Boyd and the young girl are gone. Billy returns to the United States but is driven to return in search of his brother. He's told where Boyd's body is buried and learns that Boyd had shot two men for no apparent reason. A friend of one of the men tracked down Boyd. Billy returns his brother's body to the United States and buries him there.