The Heron Kings have been betrayed. A century after their formation from a gang of desperate peasant insurgents, the shadowy band of forest rangers suffers a rare defeat when a skirmish turns into a bloody ambush. Their shaky truce with the crown is tested as young members Linet and Aerrus work to track down their enemies. When reluctant peacetime soldier Eyvind reveals a conspiracy to welcome the charismatic invader Phynagoras, the trio must convince a weak king and pitifully few allies to stand against the storm.
Their only hope lies in the forgotten tactics of their own guerrilla past, and a terrifying new alchemical weapon the likes of which the world had never imagined. The only question is which side will be destroyed by it first...