Do any of us truly know who we are until we're tested? Having escaped Heidelberg's gallows, the occult world threatens Faust's life and livelihood once again, when his new patron's son turns out to be a faerie changeling. Faust is sent to do the impossible - take the faerie changeling, find the stolen human child, and force the faerie prince responsible to swap them back. But Faust's patron has political enemies keen to use this monstrous event as an excuse to take everything for which he's worked. Summoned to appear before the powerful Vehmic Court, Faust's patron faces execution if he can't produce his human son at his trial. With agents of the Vehmic Court close behind, and capricious faeries ahead, Faust, Wagner, and the young changeling Lorenz - necromancer, werewolf, and faerie - face questions about their own identities, and their places in an ever more complex and dangerous world.