On the endless, miles-high expanse of prairie grasses known as the Forever Sea, magical ships sail the surface, harvesting resources to support the pokets of human civilisation that eke out an existence in this perilous world.

Kindred Greyreach is a hearthfire keeper - a mage who wields the power of her voice and shapes the bones of past captains to keep her vessel afloat. She has just begun to settle into life aboard her new ship, The Errant, when she receives devastating news: her grandmother, The Marchess, legendary captain and unmatched keeper, has disappeared into the sea.

Though most are convinced that the Marchess is dead, Kindred believes her grandmother is alive, seeking something in the depths. To find her, Kindred will sacrifice nearly everything, navigating the perils of a world on the brink of conflict, where a water war simmers, a mythic pirate city floats beyond safe seas, and beasts lurk in the deep.

And beneath it all, there glimmers the elusive promise of a world beneath the waves.