In the winter of 1578, warlord Araki Murashige has rebelled against Oda Nobunaga and barricaded himself inside Arioka Castle. A series of troubling incidents within the besieged stronghold creates mysteries his own retainers cannot solve. His most promising source of insight is also his prisoner: Kuroda Kanbei, one of Nobunaga’s gifted strategists, held in the castle dungeon. Enemy and captive are forced into an unusual intellectual partnership while war and suspicion close in around them.