Born into a wealthy family, probiator Simeon Noktis tries to make amends for past sins by protecting the weak in the district of Blizhnyestal. But the enormous city of Varanganthua doesn’t care about its residents. In the neutral zone between Blizhnyestal and the Adeptus Mechanicus enclave—Steelcairn—people find a corpse split in half. Simeon is assigned the most dangerous investigation of his entire service. In cooperation with the tech-priestess Ro-1 Lyuks from the Collegium Extremis, the probiator Noktis plunges into a grim world of techno-heresy, illegal servitors, and unlawful exploitation—one that can end his career—or his life.