The movie opens in a flashback where we see the Man (Viggo Mortensen) in bed with his wife (Charlize Theron). The man wakes up to a sound and a glow coming from outside the window of their room. He walks to the window and looks out. In a hurry, he then runs into the bathroom where he begins to fill the sink and bathtub. His wife wakes up and comes into the bathroom. She asks him why he is taking a shower, but answers that this is not what the water is for. She then looks outside to see what he saw. The scene then cuts to the present where the man is walking with his son down a snow-covered road.
As the Man and his son are walking, we hear a narration by the Man explaining that he no longer keeps track of time. He further explains (in a very vague way) that a few years ago at 1:17, there was a bright flash in the sky followed by rumbling sounds and that was when time stopped. As the Man and his son walk and search abandoned cars, the narration continues. He then says that the sun has not come out for a long time; the weather is getting colder and greyer every day. He then says the things he fears the most are cannibals and hunger. They are walking to the coast and heading south to see if things are warmer and better there.
The Man and his son stop at a car in the road and make camp. While they sit in the car talking, we see that the Man has a pistol with 2 rounds remaining and a shopping cart full of things they have collected. The two talk about the boy’s mother, making it clear that she has been dead for a significant time. The Man also explains to the son how to kill himself the right way with the gun, and that the remaining 2 bullets are for themselves. As they continue their journey, we see several flashbacks to the Man and his wife. We witness her giving birth to their son and that she reluctantly did so, apparently aware that the life they would give him would be hopeless. Right then the flashback ends as the man wakes up suddenly to the sound of a truck in the distance. He wakes his son and they run out of the truck they were sleeping in into the nearby woods, leaving the cart. They jump and hide in a ditch. From the tunnel emerges a large truck carrying several armed men. One stranger walks very close to the hiding Man and his son, and stops to urinate on a tree. He notice the father and son and tries to lure them to the truck, stating that they eat “Whatever we can find”. The Man points the gun at the stranger and tells him to not look back at the men he came with or that he will shoot. He refuses and calls the Man’s bluff. As the noise of the truck startles the Man, the stranger jumps and grabs the son, holding him at knifepoint. The Man shoots the stranger in the head, grabs his son and runs into the woods hiding over night avoiding the group who were looking for them.
The next morning, the Man and his son go back for the cart. The contents of their cart have been pillaged. While the Man gathers the remainer of his things, he notices a pile of intenstines, as well as the clothing and severed head of the man that was killed the day before. It is evident that the men in the truck would have eaten our protagonists had they came out into the open. In a flashback, we see the Man and his wife talking about killing themselves like the other families in the area. She says that eventually they will be caught, that she and their son be raped, that all three will be murdered and eaten. He says that she needs to be strong and stop talking about this bleak scenario. She says that they only have 2 bullets left and that they should use them now. Unable to deal with her bleak outlook on the future, he leaves the room. Returning to the main story, the Man and rest by their campfire. The son asks if they are still the good guys. The Man explains that they are always going to be the good guys, and they are carrying the fire inside themselves.
Back on the road, the man and his son rest in an abandonned truck. The son mentions that he sometimes wishes that he was dead, partially so he could be with his mother. Telling his son that he shouldn’t be thinking or talking about her too much, the man contemplates some of the last memories of his wife. In the morning, the Man wakes up and walks to the edge of the bridge where he takes a wallet out of his jacket with a picture of his wife in it. He throws it over the bridge and leaves his wedding ring behind. We get another flashback of the Man and his wife talking. She has given up all hope and has decided to comitt suicide. He begs her to stay another night. She blames the man for not letting her die earlier and walks outside without saying goodbye to the son. She takes off her jacket and outer clothing and walks off into the dark to die.
The two walk on and see a large house in the distance. After looking at it through binoculars, they decide to go into the home. In the main room, they notice a large pile of shoes. The Man is very confused and goes into the kitchen where he sees a large door in the floor, closed via padlock. They break in and go down into the cellar. They hear something in the darkness and when they get close, a naked man comes into the light. As they attempt to leave, they see that the naked man is not alone. An entire group of malnourished people, some missing limbs beg them for help. They fight off the desperate captives and block the door with a heavy table. As they are about to leave, the owners of the house return. The Man and his son run upstairs and hide in a bathroom. As one of the captors approaches, the father points the gun at his son’s head to protect him from the cannibals. Luckily for them, the cannibals are distracted by the captives attempting to make an escape. In the commotion, the Man and his son run out and quickly hide while the people in the home try to find them. As night falls, they hear the screams of someone being butchered.
As they are walking, they find the neighborhood where the Man grew up and he takes a moment to visit his boyhood home. While waiting outside, the son briefly sees a boy across the street. He runs to see him, but is caught by his father. They leave, once again heading south, the boy lamenting the fact that he is probably the only boy left alive.
Having run out of food, the two come across another home on the road. They rummage through the house and find the remains of a man who died in bed. Having lost hope, they stumble upon an unlooted bomb shelter in the back yard. Finding ample food and supplies inside, they eat, clean themselves up and make home in the new shelter. One night, they hear noises above. The noise sounds like a dog, meaning that the area is no longer safe. They stock up food in a pull cart and head out the next morning.
As they are walking, they see an old man (Robert Duvall) walking. They approach him very carefully and see that he is no threat. The boy wants to bring him along and the Man says no, but he allows the old man to eat dinner with them. As they eat and talk, the old man says that he thought the boy was an angel and he never thought he would see a child again. They continue to talk and then go to sleep. The next day the Man and the son are on their way alone again.
While the Man and the son continue, they go into the woods and leave the cart because they see a series of wooden huts. As they walk closer, the Man sees a row of spears with human skulls and other human remains on the ground. Quickly turning the other way, they see a fresh pile of blood-soaked snow.In the distance, a woman and a child are being chased by a band of cannibals. The Man and the son get away while we hear the dying screams of the woman. This frightful sight is followed by a small earthquake. Multiple trees almost hit them and they take cover and hide. After the dust has settled, they get back to the road once again.
After they Man and son wake up from camp, we see that the Man is growing sicker. They talk about how they are close to the ocean. Arriving, they are both disappointed at the receding beach, which is littered with garbage and debris. The ocean, which the boy had hoped would be blue, is a muddy brown. They walk to the water and look at a crashed boat about 200 yards into the surf. Hoping to find something useful inside the wreck, the man leaves his son with the revolver in their makeshift tent. The son falls asleep and we see a stranger with a knife walk up to the tent. The next shot is of the Man swimming back to shore with a flare gun from the boat. He puts on his clothes and goes running to his son. All of their supplies are gone, but the son is not harmed. The thief took everything including the Mans shoes. Cursing, the man is determined to retrieve their belongings.
As the Man carries his son, they see the thief with their cart in the distance. The Man takes the pistol and runs after the thief. The Man proceeds to take back his belongings and rob the thief, taking his knife, his clothes and his shoes. The son begs his father to have mercy on the man, but he refuses. Back on the beach, the boy is very upset and sulks, eventually convincing his father to return the stolen belongings to their owner. They go back and try to find the thief, but he is nowhere to be seen. They leave his clothes in apile, along with a can of food.The Man and his son continue walking.
They start walking through a street lined with homes. It is quiet and they find a tin with a live bug inside. While it flies away, they both stare at it in amazement. Distracted, the Man does not notice an archer across the street and gets hit in the leg. They jump to take cover and the Man retaliates with his flare gun. We hear screaming from the room and the wounded Man goes running to see who is inside. He gets in the room where he sees a woman who is sitting over the stranger who shot him. The archer is dead and the woman accompanying him weeps. Our heroes bandage up the man’s leg as best they can, leaving the woman.
The Man and his son go walking back to the ocean and the man stops. He says he can no longer pull the cart. They take a bag full of the food and they head to a sandy spot of the beach. They make camp and the man, realizing that he is dying dreams of his wife. We see what life was like prior to the world ending. He wakes up to his son talking to him. The Man knows he is going to die soon, and he tells his son to continue on south. He says to remember the things he has taught him and to keep going like they have been. The son says he wants to die with his father, but the Man says that he cannot. He says that his whole heart is in his son and he has to go on. He then falls asleep and dies.
After a period of mourning, the son looks at his father, reaches into his jacket and takes his binoculars. He then covers the Man with a blanket, puts the pistol with single round into his belt and begins walking along the shoreline. In the distance, we see a stranger (Guy Pierce) walking toward the son. The son points his gun towards the stranger, but amazingly, the man does not reciprocate. He tells the boy that he is not a cannibal and that he is “one of the good guys”. The stranger asks the son who the man on the beach is and the son explains that it was his father. The stranger explains to the boy that he now has 2 choices. Either go on his own, avoiding the roads or joining him and the others that he is travelling with.The son asks if he has any children, to which the answer says “a boy and a girl”. Asking if he is carrying the fire inside, to which the stranger does not know how to answer, the boy decides to join them. Saying goodbye to his father one last time, the son walks to the stranger. We see that he is with a woman (Molly Parker) and 2 children, a boy and a girl. The boy was the one the Son spotted earlier by his father’s childhood home. We learn that this family has been following the boy for some time, and that the dog they heard earlier at the bomb shelter was their companion. He is assured that he no longer has anything to worry about.