Six years have passed since the suppression of the Eighteen’s Circle uprising. The Black Squad, still serving Lady, has for all those years been moving without stopping through the territory of her empire—finishing off surviving groups of rebels and preventing attempts at new uprisings. And now, while pursuing yet another such group, several men from the Squad arrive in the far north, in the city of Archu. But it turns out the situation there is far more serious than anyone assumed—beside the city rises a mysterious black castle, steadily increasing in size. What’s more, it turns out that in Archu there is also Raven—a deserter from the Squad—who, even if out of ignorance, put a great deal of effort into the growth of this castle. And when the castle reaches the needed size, its inhabitants will be able to free the Lord—the former ruler of the empire and Lady’s husband, who was once betrayed by her.