Rescue captain Owen awakens Mara, the last mermaid, with a kiss in the aftermath of an explosion, only to be seen by her as the "son of the family that destroyed her people." With the "King Tide" just twenty-one days away, the Thorne family's greedy experiments are brewing a cataclysm that threatens to wipe out both the merfolk and the human harbor. To save both worlds, these sworn enemies are forced into an alliance. Bound by a mysterious "Tide Mark" that forces them to share heartbeats and agony, their life-and-death struggles begin to unravel the cruel truth behind a twelve-year-old tragedy. As the blade of hatred is deflected, a profound cross-species bond quietly takes root. They must reclaim the sacred artifact before a colossal wave swallows everything, using love and sacrifice to fight for a chance at coexistence for both worlds.
