Three months ago, Anton Olsson found a buried jewellery box in his allotment garden. He handed the box to the police, but after no one claimed it, it became his. Last week, a horrifying discovery was made. Someone had broken into Anton’s house and stolen parts of his valuable jewellery collection. This exciting mystery will test the skills of Moa and Måns as they use their detective skills and the secret language of The Secret Club to solve the case.