In the ancient city of York, a master charm has been stolen - one powerful enough to raise an army of metal guardians across the country. Built to protect, they can just as easily destroy, and in the wrong hands, they will. Which is bad enough. But if the charm isn't recovered soon, they won't be the only ones on the rampage. Because Heather - near-goddess of the wood and wild, and deeply unimpressed partner of the charm's creator - will tear the city apart to stop them. DI Adams never asked to be the magical community's go-to fixer, but with York on the brink of collapse, she's the only one standing between humanity and a full-blown nature-vs-machine catastrophe. Armed with her invisible, caffeine-addicted dog, her duck, and a bunch of Folk with more opinions than usefulness, Adams descends into the hidden underworld of York. There, she'll face light-fearing gerbils, ravenous beasts, and allies with questionable loyalties. And let's not mention unstable dimensions and reality playing fast and loose with physics. But she's got no time to learn how to navigate any of it. Time's running out. The charm is waking. And when tree and root rise to meet steel and iron, nothing will survive the collision. . .