Marine biologist Hannah Bowman once loved the sea, but when it took everything from her, she walked away from it. However, she didn't walk far enough away. Estranged from the ocean, Hannah, now lives alone in a cottage on the grounds of a decommissioned lighthouse in her hometown of, Stone Harbor. A barista by day, Hannah has few friends. A recluse by night, Hannah's sleep is plagued by nightmares. For three years, she has resisted the lure of the sea. But Hannah Bowman's self-imposed exile ends in a wave of unforgettable terror when the Spines of the Deep come calling.