An unidentified thing came down to Earth and met the very first stimuli it will take shape from.
At first, "It" took the form of a sphere that could imitate anything that existed. Sometime after being dropped onto the Earth, It assumed the form of a rock and once temperatures began to rise, It copied the appearance of moss. Before long, as snow began to fall, a single wolf came ambling from the south and, once it collapsed, "It" took the form of that creature. Having gained a consciousness "It", now in the form of a wolf, continued walking and carving into its mind new sensations.
Meeting the Nameless Boy
After walking for an unknown amount of time, the wolf comes across a boy. The nameless boy, calling the wolf "Johan", is very excited to see it and is very happy it didn't forget about him. Noticing that Johan isn't acting normal, the boy carries it into the house where he tries to give it food, but to no avail. Once inside, "Johan" takes in the atmosphere of the house - observing the sounds, the smell, and the warmth. If It could speak, It would probably say "I want to stay here forever".
The next morning, after trying (and failing) once again to feed Johan, the boy and the wolf go out to gather wood. Besides the boy, there are no people to be found and the only thing outside is houses that have long since fallen into ruin. The boy cuts and gathers the wood from a nearby house, telling Johan it's like borrowing from other people. But he expresses guilt, saying he knows, deep down, that if the others were to come back they would probably be angry at him. He understands though that if he doesn't do this, he will die. He holds hope that the other people of his village will come back even though they've been gone for five years.
The boy mentions that the villagers left in search of a paradise with food and people. In that paradise, there are many types of fish and "things they call 'fruit.'" He tells Johan how much he would have liked to go with them and recalls trying to sneak out and follow them, but Johan stopped him by biting his leg. As a result, the other villagers told him he should stay back and take care of his grandparents, but that they would be back with souvenirs when they found the place.
After gathering wood, they head back to the house and the boy hears a noise coming from inside. Before opening the door, he silently hopes and pleads that the noise he hears is from one of the villagers. However, he soon finds out that the noise was actually the result of a fish on the end of the fishing line attached to his home. The boy retrieves the fish and, to save fuel, they decide to eat it raw. Noticing that Johan is refusing to eat for the third time, the boy wonders if the wolf has forgotten how. He shows it how to eat and the wolf immediately mimics the boy's actions.
Later that night, the boy draws pictures of the other villagers on the wall. He explains to Johan that he is doing this so he doesn't forget about the people that lived there. He then tells Johan that he is thinking of leaving because he wants to see the world and experience new things, even the bad things that will undoubtedly happen. The boy spends all of the next days preparing for the journey and, once he is finally done, they head south. After hours of walking, they come across a marker that tells them to continue heading forward and they decide to rest for the night.
While eating dinner, the boy says he can't wait to eat something else besides fish and that he would love to try eating things like fruits and vegetables. The two continue on their journey, finding more and more markers. After about five days, the boy finds a bush that he says proves they are getting closer to the mountains and, just as they are about to continue, the boy slips and falls into the water, injuring his left leg. They decide to stop for the day so the boy can tend to his injury. He tries to reassure himself that it is just a flesh wound and that he can keep going.
As the days pass, it is obvious the boy is losing strength, as he cannot continue walking for long periods of time, and his injury is starting to swell. He continues to try and convince himself that turning back now would be foolish and that surely they don't have much farther to go. Just as he says this, the boy spots a marker with a crossed-out arrow, telling them that going forward will not lead to paradise. To the left, the boy sees broken down wagons and multiple headstones. The boy, trying to remain optimistic, tells Johan that everyone got this far, which means paradise can't be far away now. Breaking down into tears, the boy asks Johan if they can make it to the mountains but, when the wolf doesn't respond, he becomes frustrated wondering why it doesn't answer him. He continues crying even harder, knowing that Johan can't respond and that he's been talking to himself the whole time. He apologizes and decides that going home would be the best thing to do.
Once home, the boy cries himself to sleep and awakes the next morning with a fever. He makes Johan food and checks on his wound, which is now infected. He tells himself that his wound is healing and that once it heals, they will try to find the mountains again. However, the boy's fever is even worse the next day and he has no strength to get out of bed. Later that night, he struggles to get to his chair, saying "If I'm sleeping when they all come back, that would be embarrassing, right?" He asks Johan to never forget about him and quietly lays back in his chair.
The next scene with the boy shows him meeting up with all of the other villagers and traveling to find the mountains. They eventually reach their paradise where they find other people.
After an unknown amount of time, the boy's body falls to the ground. The wolf tries to get him to move but is unsuccessful. It grabs ahold of the boy's coat and immediately begins taking on the form of the boy. It leaves in search of "an even stronger impetus" and will no doubt fulfill the boy's wish of exploring the world.