About the Book: A few months after returning from the depths of Tartarus, the demigods Nico di Angelo and Will Solace head out to join Nico’s half-sister Hazel Levesque at Camp Jupiter to manage a crisis of their own making. Monsters of the Underworld, shown they have choice, now seek refuge at the camp. But when some begin disappearing and a dark force emerges—one tied intimately to each of them—the stakes grow deadly.