Arthur Penhaligon managed to take away the five Keys from their immortal guardians, but taking possession of the Sixth Key is not an easy task. Excellent Saturday is not just one of the Confidants, she is the oldest Resident and the most powerful witch in the House. And everything that is now happening around the Rightful Heir seems to be part of a plan that she has been overseeing for ten thousand years. Arthur is besieged from all sides: his hometown is attacked, the House is collapsing, and his allies are completely unreliable. The Heir simply needs to penetrate the impregnable Upper House, because only the power of the Keys can prevent what is happening. But even if Arthur manages to take possession of the Sixth Key, will this be enough to resist the witchcraft hordes of Saturday and prevent her from completely seizing power?