In the wake of the events of Black Tide Son, Hart flees into pirate-infested waters to shelter on the island where former rogue James Demery and the Fleetbreaker, Anne Firth, now rule.

Reeling from their discoveries about the truths of the Mereish-Aeadine war, Mary and Samuel hover on the precipice of a terrible, world-altering choice—they can stay silent and maintain their good names, or they can speak out and risk igniting total war across the Winter Sea.

Meanwhile, Benedict captains The Red Tempest, a lawless ship of deserters and corrupted mages in search of an Usti spy with incendiary stolen documents. Benedict is determined to make the truth known, consequences be damned.

As rumours spread of a new Ghistwold sprouting in the Mereish South Isles, Mary and Samuel sail once more into intrigue, espionage and an ocean on the brink of exploding into conflict. They must chart a course toward lasting, final peace, at the heart of the age-old battle for power upon the Winter Sea.