Mathias and his sister Malin are taken on an overnight trip to a nature reserve by their eager, nature-loving father. But their father’s new girlfriend Ella Loudmouth and her daughter Birgitte are also coming along on the trip. The atmosphere is already grim from the time they’re in the car and Mathias foresees forced jollity with the bonus family out in the wilderness where there’s nothing to do. But it’s not long before mysterious things start to happen and Mathias receives a message saying that Malin is in danger. There turn out to be creatures living in the forest that are invisible to humans, unless they do what Mathias does: go through an uprooted tree and come out on the other side into a place where there are pixies and elves and a river sprite on the lookout for human food. Mathias faces enormous trials and the trip proves to be anything but boring.

Sigbjørn Mostue has written a super intense novel for 9–12-year-olds that combines mythical creatures from Norwegian folklore with modern-day problems of conservation and climate issues.
The book is illustrated by Ketil Bleidin.