London is a ruin, destroyed by German bombs, ravaged by the Horologia virus, and ruled by the ruthless Captain Hanz Otto Oswald Kretschmer, whose Marauders search for and seize the children who are immune to the virus in the hope that their blood will produce a cure. Their latest victim is sixteen-year-old Gwen Darling's younger sister and Gwen will do anything to get her back, even join up with Pete and his gang of Lost Boys living in a city hidden...

Bella, Gwen, and the Lost Boys have escaped to Alnwick Castle, but it is not the safe haven they hoped it would be for the "cure" for the Horologia virus has mutated into something even worse--so the Duchess Alyssa and Maddox Hadder set out searching for the virus's origin, an extinct poisonous apple, supposedly from a tree at the center of a labyrinth hidden deep within Germany and guarded by monsters.