After Siloé and her half-brothers unexpectedly entered the Hexaworld, Nola learned a lot about her mother and the history of Pandorient. But the unanswered questions multiply when she discovers a strange key at home. A key that Nola has seen before... in Annah's book! What could it possibly open? To find out, she immediately returns to Pandorient. But soon, a disturbing disappearance leads Nola, Igor, and Andréa into an investigation which may turn life in Pandorient upside down...