For centuries, the isolated island of Blackwater has guarded a secret buried beneath its dark waters. When night falls, ancient creatures emerge from the sea to feed-but their hunger has long been restrained by an agreement made between the islanders and the terrifying being known only as the Father. The terms are simple. The agreement must be honored. The creatures must remain satisfied. And outsiders must never discover the truth. But when strangers become stranded on Blackwater, the fragile covenant begins to unravel. The bells ring, the villagers lock their doors, and something enormous awakens beneath the sea. On Blackwater, breaking an agreement carries a terrible price-and the Father has come to collect.