Twelve-year-old Zak Killian is hearing a voice. Could it be a guardian angel? A ghost? No, that's crazy. But sometimes the voice is so real. . . . It warns him of danger.One day Zak is standing on the subway platform when the tunnel starts to fill with water. He sees it before anyone else. The voice warns him to run. His friends Moira and Khalid believe this is more than a premonition, and soon all three find themselves in an alternate universe that is both familiar and seriously strange. As Zak unravels the mystery behind the voice, he faces decisions that may mean the end of their world at home - if they can even get home!In his most propulsive and heartfelt book yet, acclaimed author Barry Lyga explores the depths of friendship, the bonds of family, and the nature of the universe itself.