The Mercian Free Ports are the only confederacy yet to fall. Their only land link to the southern continent, a long and narrow isthmus, is protected by the city of Bar-Khos. For ten years now, the great southern walls of Bar-Khos have been besieged by the Imperial Fourth Army.

Ash is a member of an elite group of assassins, the Rōshun - who offer protection through the threat of vendetta. Forced by his ailing health to take on an apprentice, he chooses Nico, a young man living in the besieged city of Bar-Khos. At the time, Nico is hungry, desperate, and alone in a city that finds itself teetering on the brink.

When the Holy Matriarch’s son deliberately murders a woman under the protection of the Rōshun; he forces the sect to seek his life in retribution. As Ash and his young apprentice set out to fulfil the Rōshun orders – their journey takes them into the heart of the conflict between the Empire and the Free Ports . . . into bloodshed and death.