Clark and Summer, a young married couple, are on their way to see Summer's parents when a sudden tire blowout forces them to abandon the car and press on on foot in search of help. They come across a small cluster of weathered buildings and quickly realize the town is eerily deserted, with an unsettling silence hanging over the place. A drifter in a wide-crowned cowboy hat arrives, introducing himself as Joseph, and his arrival immediately casts a shadow over Clark with his confident, magnetic presence. That first night, around a flickering campfire, the trio talks in drawn-out, uneasy phrases. Summer shows Joseph a photograph of her older son, Ben, who is Clark's stepson, and Joseph’s response hints at a philosophy that rejects social conformity in favor of a higher calling.
The next morning, Joseph suggests that he and Clark walk back to the car to siphon off the fuel, then drive to Joseph’s truck to leave the area altogether. Summer wishes to accompany them, but both Joseph and Clark insist that, given her delicate condition, she should stay behind. Joseph produces a revolver and begins to teach Summer how to use it, and the lesson slides into an intimate, inappropriate moment. Clark’s anger is palpable, yet he and Joseph still head off together. Along the way, Joseph mocks Clark for his perceived weaknesses and proclaims a knowledge of him that feels invasive. Clark grows convinced that Joseph is a fanatic, a religious zealot in disguise.
When they reach the town’s edge, Joseph tells Clark that what he is about to endure is his own fault because of his sins, then vanishes. Clark opens the trunk of his car and discovers Ben in a rotting state, swarming with flies. The sight horrifies him, and a rush of panic makes him realize Summer is now alone back in the abandoned place, forcing him to hurry back.
Meanwhile, Summer finds a room in one of the deserted buildings where photographs line the walls, including her own photo of Ben with a cross scratched over his face. She turns to discover Joseph is in the room with her. The gun he gave her is unloaded, and he subdues her, using a razor to carve a cross into her forehead, insisting that the mark will stay and that she will remember this moment. She pleads for an explanation, and he claims it is God’s will. Just then, Clark arrives and attacks Joseph, beating him until he is subdued.
When Joseph regains consciousness, he is tied to a chair. Clark demands to know how they can escape the town, but Joseph refuses to speak. Clark resorts to a brutal measure, using pliers to remove one of Joseph’s fingers in order to compel him to talk. At last Joseph concedes that he is an avenging angel, sent to punish the wicked for their sins. He offers to reveal what was in the trunk, but Clark insists it was nothing. Joseph then proposes that they follow him to a spot by the river to show them something more. Just beyond the water tower lies a field of rough wooden crosses marking graves, and Summer asks whether Joseph killed all those people; he denies it, saying they died by their own hands and that every one of them deserved it.
Further into the graveyard, three empty graves stand out. Joseph presses Clark to tell Summer what his sin is, but Clark refuses. In response, Joseph hands the gun to Summer and repeats the instruction to cock and shoot if she chooses. With no clear answer, Summer believes the blow has something to do with Ben and at last fires. Clark collapses as Summer asks what she did to deserve this pain; Joseph replies that her sin is apathy—knowing something is wrong but taking no action.
Joseph raises his hand toward the sky and, miraculously, his finger reappears and his face is restored. He leaves Summer at the graveyard, the gun still in her grip, and walks away. Summer tries to shoot herself, but discovers there is only a single bullet in the chamber, leaving her with a bleak silence and a memory that cannot be erased.
