Witch’s apprentice Bridey Corkill has hated the ocean ever since she watched her granddad dive in and drown with a smile on his face. So when a dead girl rolls in with the tide in the summer of 1913, sixteen-year-old Bridey suspects that whatever compelled her granddad to leap into the sea has made its return to the Isle of Man.

Soon, villagers are vanishing in the night, but no one shares Bridey’s suspicions about the sea. No one but the island’s witch, who isn’t as frightening as she first appears, and the handsome dark-haired lad Bridey rescues from a grim and watery fate. The cause of the deep gashes in Fynn’s stomach and his lost memories are, like the recent disappearances, a mystery well-guarded by the sea. In exchange for saving his life, Fynn teaches Bridey to master her fear of the water — stealing her heart in the process.

Now, Bridey must work with the Isle’s eccentric witch and the boy she isn’t sure she can trust — because if she can’t uncover the truth about the ancient evil in the water, everyone she loves will walk into the sea, never to return.