It’s Sophus Blix’ 15th birthday, and his uncle, the owner of an antiquarian bookshop, gives him a present: He can choose any book he wants in the shop. Sophus isn’t really interested in books, but hidden in the basement he finds an old, beautifully bound book which turns out to contain a big secret.

Then Sophus notices that things are starting to happen, and his uncle tells him that he is a chosen one, a guardian. Sophus doesn’t want to be anybody but himself, but soon he is forced to decide how to act. The book is actually a kind of code to a treasure that more people are interested in, and soon he finds himself in a dangerous race to get to the treasure first.