hansel and gretel

Eun-soo, a salesman, is driving his car along Highway 69 while talking on the phone with his four-weeks pregnant girlfriend, Hae-young. She tells him to stay by her side for the remainder of her pregnancy, but he replies that his mother is ill and he has to visit her, leading to a quarrel as Eun-soo is driving and causing him to hit a rock and pass out. He wakes up to find himself stranded in a dark forest. He sees light from a lantern that a young girl is carrying. She introduces herself as Young-hee as they head for her house, a large house in the middle of the forest called the "House of Happy Children".
Her parents, older brother Man-bok and younger sister Jung-soon are waiting on the porch when they arrive. Eun-soo finds the children following his every move the following day. He decides to leave, but returns because it is getting dark. As he tries to leave again, he discovers that the parents are leaving, and they tell him to take care of the kids.
He soon learns from their mother, who is hiding in the attic, that they are not the children's real parents. Their car broke down on Highway 69 too, and they met Jung-soon when they explored the woods. She tells him not to believe the children. As Eun-soo makes his way out again the next day, he sees Man-bok and a couple approaching the house. The man, Byun is a seemingly amicable deacon while his wife has a malicious aura about her. Eun-soo keeps looking for clues, finding that the meat they had consumed was actually the flesh of the missing 'father' and his wife had turned into a china doll. He also notices that Byun's wife had disappeared after accusing Jung-soon for stealing her ring. At night, he secretly follows Man-bok into the woods, making a trail of breadcrumbs so he wouldn't get lost. He realizes Byun's wife had turned into an oak tree.
Man-bok stops in front of a mysterious door to a room, putting down the notebook that the siblings have been working on throughout the movie. His face changes to an old man's face as he passes the door. When he leaves, Eun-soo enters the room and looks over the notebook's contents, finding out that the children are over thirty years old. Suddenly Young-hee comes in sleepwalking, and as they talk, Eun-soo looks at her face which has become an old woman's. Eun-soo backs in shock, hitting bookcases in the room and causing notes to fall off the shelves. As he reads the notes, the reason Man-bok wanted to get rid of the couple who used to be his 'parents' is revealed. The husband did nothing but quarrel with his wife when Jung-soon accidentally stepped on shards of broken glass while playing, angering Man-bok who used his powers to cut the husband's fingers and drop them into the boiling pan. Since their awareness of Man-bok's powers, the couple tried not to mess up, or they would end up dead.
Eun-soo sees more of the children's drawings in the notebook, such as a woman with mutilated limbs, a woman turned into an oak tree, a woman in a dress with red crayons splattered on her face and a man resembling himself laying on the grass beside the red flowers he had seen on his way out. He realizes that the last depiction foretells his end and is determined stop the children before they murder him.
Meanwhile, Young-hee returns to the house upon hearing Byun singing. Eun-soo heads back too and learns that Byun is a religious cult leader trying to kill the children, and he is holding Jung-soon hostage. He knocks Byun out and listens to the children's side of the story from Young-hee in the form of a flashback.
The kids lived in an orphanage called the "House of Happy Children". The abusive caretaker raped the girls and beat the boys. Man-bok tried to save his friend Seung-ho from being beaten for spilling food, but he failed and Seung-ho was locked in a dark room. Young-hee and Jung-soon once tried to escape but came back, ending in Young-hee going into the caretaker's room to save Jung-soon from being raped. One Christmas Eve, they wondered if Santa Claus would give them presents, because they thought they weren't good that year. This led to Man-bok activating his powers, which he only realized the next morning when Santa Claus did come and told the siblings that their wishes could come true just by imagining it, and he gave them a Hansel and Gretel storybook. They believed they must reenact the story to all bad adults. The three of them then witnessed Seung-ho being forced into a sack, where he was beaten to death. Man-bok felt that this must stop. They sneaked up to the locked room which Man-bok unlocked just by imagining it. They tried to give candy to their friends inside but realized that they were all dead. The caretaker found them and was going to burn them in the fireplace, but Man-bok screamed, bringing the story back to the present as he screams when Byun rises to kill Eun-soo, causing a whirlwind in both the flashback and the present which throws the caretaker into the fireplace, and Byun is stabbed to death.
The winds stop and the children ask Eun-soo to stay with them. Eun-soo rejects them for his loved ones and suggests taking the children outside with him. The children refuse, saying adults will always be bad. Eun-soo argues that if they continued their doings, they would be bad adults too. Young-hee suddenly whispers, "Burn the notebook, so you can get out of here." He does so before Man-bok can stop him, and Eun-soo glances at the crying children as the book burns.
Eun-soo wakes up in the location Young-hee found him at. He walks up the road and sees the police, who tell him the tragic stories of Highway 69, and that they are amazed at his survival.
A year later on Christmas, Eun-soo has married Hae-young, and they have a baby boy. Hae-young asks Eun-soo to go buy milk. As he goes out, he wonders if his encounter was real or if it was a dream. His collection of news clippings of Deacon Byun (now revealed to be a serial killer and religious cult leader) who is apparently missing suggests that it was real. He comes across the same notebook that the children used and browses it. The pages are blank until the last page, which shows three children dressed like Man-bok, Young-hee, and Jung-soon all holding hands and smiling. The children had given up and realized that they didn't need parents to be a family. Eun-soo looks out the window and outside in the snow, Man-bok, Young-hee, and Jung-soon turn around and make their way back into the woods.