Sometimes one hero isn't enough - sometimes you need a full dozen. Mack's search for his dazzling dozen continues in the fourth instalment of this funny, action-packed fantasy series by the New York Times bestselling author of GONE. Time is running out for Mack MacAvoy and the magnifica! It seems the only way they can defeat the Pale Queen and her evil daughter Risky is to learn the magical language of Vargran. So Mack, Jarrah, Xiao, Dietmar and Stephan travel to Europe to find the Key, an engraved stone that unlocks the power of Vargran. But can they locate the invisible castle of William 'Blisterthongö? MacGuffin, who guards the Key? (Yeah, we said Blisterthong. Yeah, it's as painful as it sounds.) Mack has less than 30 days to master Vargran, round up the rest of the magnifica, and defeat Princess Risky. Will The Key be enough? Or is there something else Mack must find in order to save the world?