The world is changed, poisoned. The seas flood the land. Trin is part of a team defying the stormy sea at the new coastline to heal the ocean. Now Trin hears voices from the stormy sea. Is she sick or crazy? Rilla has lived hidden deep in the ocean all her life. Challenging her father's rulings, she will take the catalyst to transform and ascend, leaving the world of the Abrax forever so she can help the walkers heal Mother Ocean. When two strangers arrive on the high-tide, Trin and Rilla's lives will change forever. Their fates will be intertwined in the place between two worlds.