Police Constable Peter Grant investigates the supernatural related murder of an American in the London Underground. Peter Grant is a young police constable and wizard in training for the semi-secret section of the London police department known as the Folly, that deals with magical and supernatural problems.
The story starts soon after the events in the previous book in the series, Moon Over Soho, during which an evil wizard known only as the Faceless One nearly killed Grant. Grant and his boss, Detective Chief Inspector Thomas Nightingale are looking into the identity of this wizard.
Lesley May, Grant's old partner from his days in the regular police, was injured on an earlier case involving magic and now has to wear a mask to cover the ruins of her face. She is on indefinite medical leave from her old job and is now learning magic as well at the Folly.
Thirteen year old Abigail, a neighborhood girl who knows that Grant does magic, tells him that she's seen a ghost. Grant and Lesley go investigate and see him as well, the ghost of a boy who gets hit by a ghost train while trying to spray paint a the tunnel wall.
Grant gets a call from Detective Inspector Stephanopoulos of the Murder Squad to consult on a murder at the Baker Street Underground station. A man has been stabbed with a shard of pottery, and Grant senses magic on it. They find a similar bowl at the victim's apartment and his roommate Zach tells them he thinks it came from the Portobello Market. Grant follows some leads with Zach but finds him cheerfully slippery and prone to lying.
Meanwhile Nightingale pursues a lead on the Faceless One. They know he was trained by a wizard who went to Oxford in the 1960s and belonged to a dining club known as the Little Crocodiles, so they start by interviewing any remaining known members of that club.
The victim from the underground turns out to be an American art student names James Gallagher. His father is a senator, so an FBI agent named Reynolds is sent to help the investigation.
Grant follows up a lead to an art exhibit Gallagher was planning to attend, by an Irish artist named Ryan Carroll. Carroll has a few pieces that incorporate pottery which has clearly been imbued with magic.
Zach, who is in trouble with some local petty criminals known as the Nolan brothers ends up staying at the Folly for safety and so Grant can keep an eye on him. When he walks in he immediately recognizes it for what it is, to Grant's surprise. It turns out Zach is half-fairy.
Meanwhile one of the old men they questioned about the Little Crocodiles has fled, leaving behind a magical booby trap. They disarm it and the evidence makes it clear it was planted by the Faceless One himself. They surmise that the old man was the one who trained him originally.
Grant and Lesley follow the Nolan boys, who they now believe are the connection between Gallagher and the magic pottery. They find the Nolan's are delivering vegetables to a house, and then loading more pottery from a warehouse. They check the pottery and find it matches the style and material of the shard used as a weapon exactly. The investigate and find that the warehouse is owned by the Beale corporation, which used to make the pottery during the days of the British Empire and also was involved in building parts of the underground system.
They go back to the house of the veggie delivery and find it is actually little more than a facade built over an illicit entrance to the London Undeground. They follow it down and are attacked by two pale, large eyed individuals, and when they try to chase them down they run into Reynolds. They eventually find their way back to the surface, and spot one of the pale individuals who they chase him down on the train platform. He uses magic to shake the ground, burying Grant in rubble and escaping.
Grant is rescued with the help of the river Tyburn, a goddess he has a contentious relationship with, and she assures him he is in her debt now.
While he's in the hospital recovering Lesley visits Grant and shares what her research has dug up; Beale, Gallagher, and Carroll are all connected through the Unbreakable Empire Pottery corporation. Their three ancestors founded the company which made the pottery and dealt in construction, though two moved to America and Ireland respectively, leaving only the Beale's behind.
Zach also visits, and accidentally lets slip that he knows the pale man who injured Grant. Realizing his slip, he takes off running but Grant and Lesley catch him and take him in for questioning.
Under questioning her reveals that the white large eyed people live underground and are known as the Quiet Ones. They have been living under the ground and making pottery for the Beale corporation since the Victorian Era.
The police, led by Grant and accompanied by Reynolds go down into the sewers to confront the Quiet People. As they talk to the underground dwellers, it comes out that James Gallagher was dating the daughter of the chief. Grant knows that Zach has a thing for her as well and momentarily considers him a suspect. Then Grant has a sudden memory of Ryan Carroll wearing gloves, and realizes he did so to hide his wounds from stabbing James.
They arrest Carroll and he admits it. He came to London to make art and got put in contact through his family connections with the Quiet People, which were a family legend to him. After he saw they used magic he asked them to teach him and he spent months learning. Although he did fine enough, when Gallagher arrived he quickly surpassed him. Carroll killed him him a simple fit of envy.
With that case sewn up, Grant and Nightingale follow up a clue as to the possible whereabouts of the Faceless One. They don't find him, but they find the deceased body of his old master, dead from old age and from years of using too much magic.
The book ends with Grant getting a call that Abigail has been picked up for vandalism. He goes to get her and she tells him she was trying to release the ghost on the train tracks by finishing his graffiti. He makes an arrangement with her to have her stay on the lookout for strange happenings and he will meet with her weekly to follow up on them. As he drives her home she tells him the last strange thing she saw; a talking for with the following message; “Tell your friends they're on the wrong side of the river.”
Best part of story, including ending:
The continuing exploration of the magical underworld is really interesting. There is not much new training for Grant, though, and the pursuit of the Faceless One gets very little time.
Best scene in story:
When Zach comes to the Folly, the interactions between the disparate personalities (including Nightingale, Lesley, and Molly the housekeeper) make for some funny scenes and some rare domesticity.
Opinion about the main character:
Grant is a funny and down to earth guy who still retains his enchantment with the reality of magic. He also seems to have found his feel somewhat and is growing more confident, he does need to stop getting injured in each book, though.