Katrin Halvorsdotter dwells on the Isle of Talisfarne beside the Siren Sea, famed for the magical fey that haunt its waters. There, Katrin studies at the prestigious abbey school her father taught at before his murder by law-breakers who hunted the fey. Though steeped in herb lore, Katrin yearns to know more about the magia of the water fey whose bones are coveted for the gifts they impart to wearers of now-illegal bone reliquaries.
Meanwhile, her brother Cyril is hoodwinked into carrying forbidden reliquaries to the Tsar’s great city, where he is caught and imprisoned. Fearing her brother will perish in the jail-city of Derevnaya, Katrin enlists the aid of a tsarina and journeys to save Cyril. Unknown to her, the duke whose trade empire is founded on trafficking reliquaries will stop at nothing to keep his doings secret. Now Katrin must rely on gifts she has kept hidden, or, along with her brother, suffer the same fate as her father.