Willett Gashade, Warren Oates, a former bounty hunter, returns to his small mining camp after a long absence and finds his slow-witted friend Coley Boyard, Will Hutchins in a state of fear. Coley explains that their partner Leland Drum, B. J. Merholz, was shot to death two days earlier by an unseen assassin—an act that may be tied to a revenge for the accidental trampling death of a little person in town, an incident that could have been caused by Gashade's brother, Coigne, James Campbell, who had hurried away from the camp just before the shooting. Coley grows increasingly paranoid, and Gashade reluctantly confiscates his friend’s gun as they try to piece together the motive behind the killing.
The following day, a young woman rides up and shoots her horse dead right outside the camp. The gunshot shatters the quick calm, sending Coley into hiding again. Gashade inspects the horse and notes that it appeared perfectly healthy, despite the woman’s claim that its leg was broken. She offers a thousand dollars to lead them to a place called Kingsley, and, though wary, Gashade begrudgingly accepts the assignment, with Coley tagging along. The woman proves rude and insulting to both men and refuses to disclose her name. They pause in Crosstree, where Gashade learns that Coigne had been seen there only a day or two earlier, guiding their uneasy journey toward an uncertain destination.
As they trudge the hot desert, a stranger dressed in black keeps a wary distance and seems to shadow them—Billy Spear, Jack Nicholson — signaling to the woman in brief bursts that hint at a shared, shadowy purpose. Coley attempts to spark conversation with the woman, but she taunts him and repeatedly dodges questions about the mission that binds them. One night, misreading Coley’s random gunshots as signals, Spear strides into their camp and joins the trio. Hired by the Woman as a gunslinger for reasons unclear, Spear remains openly suspicious and hostile toward Willett Gashade and contemptuous of Coley Boyard. Gashade cautions Coley to stay away from Spear, but the tension between the men continues to mount.
The Woman pushes the pace, riding hard until her horse collapses from exhaustion. Coley gives her his own horse, and Gashade agrees to let Coley ride with him for a while longer. When the trail grows fuzzy, the Woman asks Gashade to take the lead, and the group presses on despite fatigue. Spear and the Woman demand that Coley be left behind; under pressure, Gashade consents to the separation and promises to return for Coley. As they ride forward, Spear boasters of having killed Drum and threatens to shoot Coley if he tries to follow.
In the desert they encounter a bearded man—Bearded Man, Charles Eastman—who sits with a broken leg and tells the Woman that the person she seeks is only one day away. He offers a sip of water from a canteen, and his own missing horse is later found by Coley. The bearded man mounts the recovered horse and charges toward Spear, only for Spear to fire and kill him. Gashade buries his friend in the sand, a stark reminder of how treacherous this journey has become.
Hydration and hope run dry as all the horses die and the group trudges onward, fighting a merciless sun. Spear grows weaker, and when the moment is right, Gashade strikes. He knocks Spear unconscious and crushes the killer’s gun hand with a heavy rock, forcing Spear to stumble along under the blistering heat. Gashade then closes in on the Woman, who is trailing a man up a rock formation. The man turns out to be his look-alike brother, Coigne, and as the confrontation unfolds, the Woman shoots Coigne dead just as Gashade reaches them. He lies beside the Woman, uncertain if she is alive or dead, and whispers, "Coigne." The final image lingers on Spear, who stumbles aimlessly under the hot sun.
