...just chalk it [magic] up to pixie dust or quantum entanglement, which was the same thing as pixie dust except with the word quantum in it. [loc. 203]
Peter Grant and team are called in to investigate the murder of an American student at Baker Street tube station. The weapon is a potsherd, and Peter notices that it carries magical vestigia: clearly a case for the Folly, the Met Police department dedicated to magical crime.
There are other weird things happening on the Tube. Peter's mum's neighbour shows him a ghost caught in the act of writing graffiti: the murder victim's flatmate isn't wholly human: someone is weaponising ghosts: and there are delays on the Central Line. (Oh, wait.)
Lesley Marsh, who lost her face to Mr Punch, is back on the team,and Peter is having trouble adjusting to her mask. He's working more closely with other people, too: Kumar (British Transport Police), Stephanopoulos (Murder Squad) and Special Agent Kimberley Reynolds (FBI, and not your typical tourist). Sadly, we don't get as much of Nightingale as I would have liked, and though the Faceless Man -- lead villain for the series so far -- is definitely up to something, it's not the focus of the story.
I read this and the following three novels in a short space of time due to ill health, and I think this was my least favourite of the four. The trope of 'something uncanny in the Underground' is a familiar one -- Aaronovitch references a few other instances -- and I didn't feel this broke new ground. There's less magic than in the two preceding books: it's more of a police procedural. Often funny, and there's some more worldbuilding, but didn't quite hit the mark for me.
Stay tuned for three more Aaronovitch reviews!