The city saved them. The city was watching. In Sangara, those turn out to be the same machine.
Part Two opens with a recording: four seconds of static with something made of dark water standing inside it. The kindest voices in the last city on earth would like Mary to explain — and when she can't, they offer her a choice dressed as a courtesy: demonstrate what she is on their testing floor, or be kept somewhere quiet until they're sure. In the arena, under a gallery of glass, Mary transforms on command for the first time in her life and erases a captured war machine without moving her feet. So the city sends out one of its own — and learns less from beating her than Mary learns from how politely it's done.
Then they switch their machine off, and something in Mary crosses the floor anyway.
Steel runs like wax. Reports get written. And at the bottom of the dark, patient as ever, a sapphire fish shows her a church, a room of older stone, and a door that has been shut since before anyone was alive to shut it.