Texas, 1980; Anton Chigurh, a convicted hit man, strangles a deputy sheriff using the handcuffs he is shackled in before escaping and stealing a car after killing the driver. Chigurh likes to think of himself as a fair man, who only kills when it is necessary. To prove this, he plays a game with the clerk at a gas station and tells him that if he correctly guesses heads or tails when he flips a coin, he will be allowed to live. The clerk guesses correctly and true to his word, Chigurh doesn't kill him.
Llewelyn Moss finds a wounded Mexican man in the desert, along with several dead men and dogs and a briefcase containing two million dollars. He grabs it and runs from the scene but returns later with water for the wounded man. Two men follow him in a truck and he realizes that his life is now in danger. He manages to lose his pursuers and goes home, tells his wife to go and stay with her mother and then holes up in a motel in Del Rio where he conceals the briefcase in the air conditioning duct in his room.
Chigurh has been hired to find Moss and the money. He searches Moss's home, blowing the lock out of the door with the bolt pistol he used to kill the owner of the car earlier. Unbeknownst to Moss, there is a tracking device in the bag of money, and Chigurh is able to follow him to the motel. He kills a group of Mexicans waiting outside the room to ambush Moss when he comes out. Moss is not a stupid man and has rented a second room next to the original one. The rooms both share the air duct where her has hidden the money and he is able to retrieve it just before Chigurh checks the duct himself. He keeps moving, this time to a motel in the border town of Eagle Pass. He finds the tracking device in the briefcase, but not before Chigurh has used it to follow him.
There is a gunfight between the men; an innocent passer-by is killed, and both Moss and Chigurh are wounded. Moss heads across the border to Mexico where he hides the money among the weeds along the Rio Grande. He is in pretty bad shape himself but a traditional norteno band finds him, and takes him to the hospital.
Chigurh does not go to hospital. He cleans his wounds himself and stitches them using supplies he has stolen. He then goes in search of Carson Wells, another hired hand who has tried to persuade Moss to hand over the money in return for his life. Chigurh kills Wells and when Moss calls the hotel room to speak to Wells, Chigurh answers, telling Moss that if he does not give him the money then he will kill his wife, Carla Jean.
Moss goes back to the weeds and finds the case. He then calls Carla Jean and tells her to meet him at a motel in El Paso. He is going to give her the money and then put her into hiding but Chigurh has already figured out his plan. Carla Jean finds herself talking to Sheriff Bell, who promises that he will protect both her and her husband, but when he gets to the motel in El Paso he is too late; he hears gunshots, and sees a truck speeding away, although he cannot see who is in it. Moss is lying dead in the parking lot, and is not able to warn Carla Jean, who arrives to see her husband in a pool of blood.
Bell returns to the motel that night, and finding the lock blown off the door, realizes that Chigurh has arrived there before him. The assassin is lying in wait behind the door, having already found the money. Bell is demoralized and decides that he is going to retire. He is no match for the criminals he is now having to deal with.
Carla Jean's mother has passed away and she returns from her funeral to find the Chigurh has broken into her house and is waiting for her. He wants to make good on the threat to her life that he made her husband and asks her to save her own life by choosing heads or tails, but she refuses, and tells him that if he is going to kill her then it is entirely his choice. As Chigurh makes his escape he is involved in a car accident but bribes the two witnesses for their silence and leaves the scene quickly.
Bell, now retired, is having some crazy dreams. He has lost some money that his father has given him, but in the second dream, he and his father are riding a mountain pass togther in the snow. His father goes on ahead of him, lighting his path.
