The story begins with Tanya, the main character, in her room. We find out almost immediately that Tanya has something special about her SHE CAN SEE FAIRIES! We also find out that no one believes her, they all think she is crazy. The fairies tend to punish Tanya when she disobeys or tries to tell people about them. For this current unorthodox punishment, they flipped her room UPSIDE DOWN!
Tanya´s mother is so upset with her ramblings about fairies, and the trouble that ¨they¨ have caused That she brings Tanya to her grandmothers house for the summer. She soon comes to realize that her grandmothers house, and land, are infested with fairies. This makes Tanya a little uneasy, but she persists.
Tanya and Fabian, the groundskeepers son, are forbidden to enter the forest in which Tanya knows is filled with fairies. Soon after they are forbidden to enter, Tanya finds out about all the missing children in the forest and the town. This makes both children want to explore even more.
Tanya and Fabian assess a plan to enter the forest without the adults knowing. In the forest they find a girl who was supposed to have gone missing 50 years ago. After some research, they found a picture of a young Tanya's grandmother and the girl, looking the same age. This means that the girl hasn't aged, which also means she is trapped in the fairy relm. Later that night Tanya heard a noise in the kitchen that seems to have no source when she checked.
When Tanya looked again, she found hidden passageways. In the passageway she found a girl called Red. Red can also see fairies. She also explains the missing children in the own. They were changelings, which are sick or ugly fairy children who are exchanged for humans. Tanya and Fabian go back to the fairy relm to save the girl, come to find out she is evil.
Red comes and switches places with Tanya to save her life. The girl returns to her old age at once after Red passes. The rapid aging hits her and she dies from the overwhelming situation. Tanya realizes that her grandmother can also see fairies and they bond over that. No fairies are to be mean to Tanya now that she knows the truth, and she goes home knowing she will never be bothered by them again.