This is a paranormal novella published by Gollancz in 2018. The story is set after the fifth but before the sixth novel in the author’s Peter Grant series. This review contains spoilers.

Commuters on the Metropolitan line are reporting strange encounters, oddly dressed people who seem to be trying to deliver a message. The travelers call police, but tend to forget the whole thing before response can get there. Sergeant Jaget Kumar calls Peter Grant, investigator for London’s Special Assessment Unit (a.k.a. the Folly). Peter brings along the unit’s summer intern, his teenaged niece Abigail, plus Toby the dog for the ghost hunting operation. Can they figure out the message and lay the ghost to rest? And what about that odd child that turned up part way through the investigation?

Good points: Aaronovitch creates very warm and engaging characters. His vision of London is diverse, and the police are actually concerned about your problems—we’re sure they’re going to take care of all those things that go bump in the night. Besides that, the narrative features a lot of dry humor, beginning with the name of Grant’s unit, and continuing along in like vein. The story is engaging and carries you to a satisfying conclusion that also sets up future installments of the series.

On the not so positive side, there nothing memorable here. It’s a warm, feel-good story without anything much in the way of depth or social commentary. The diversity itself is a kind of comment, of course, but like the humor, it’s understated. As someone who doesn’t follow this series, I’d liked to have a little more background on Abigail, who seems to be positioned in this installment for a future with the police.

Three and a half stars.