When a series of environmental disasters leave a small coastal town completely underwater, fourteen-year-old Greenleigh ends up stranded with a group of teenagers in a building known only as the Tower. Cut off from civilization, they must learn how to survive in a world without any of the conveniences they once took for granted. When a power struggle develops between Leo, a charismatic but potentially dangerous outcast, and Greenleigh's older brother Ilkka, the group's reluctant leader, everyone must choose their alliances carefully. Prickly but fragile, independent yet insecure, Greenleigh is caught between her loyalty to her brother and her growing attraction toward Leo. When the group decides to leave the Tower on a dangerous journey to the only house left in town, the mysterious Lloyd mansion on top of the High Grounds, they must face not only the aftermath of the flood, but fellow survivors who prove even more dangerous than the disaster itself. With the group's immediate survival and hope for rescue at stake, Greenleigh must make choices that will determine not only whether or not she survives, but what kind of person she will be if she does.