The previous book's adventure in Herefordshire left the protagonist Peter Grant deeply involved in a relationship with Beverley Brook, the resourceful young woman who had saved him from captivity by the Faerie Queen. Beverley happens to be the tutelary goddess of Beverley Brook, a small river in South London, and can often be found swimming through its waters; when Peter comes to the bank and calls her name, she might jump naked out of the water, like a salmon, directly into his arms. Peter now spends much of his time – especially his nights – in Beverley's comfortable and spacious house on the riverbank. It is there that he gets the phone call catapulting him into the whirlwind of a new adventure. A bunch of teenagers breaking into a luxurious apartment and holding there a wild party of sex and drugs, ending with one of them dead of an overdose, is a matter for the police – but normally, not for Grant, whose very special police specialty are the cases involving magic. However, one of the teenagers involved was the daughter of a very magical creature – Cecilia Tyburn Thames aka Lady Ty, who is the goddess of the River Tyburn and the older and far stricter sister of Peter's girlfriend. Peter owes Lady Ty a favour for having once saved his life, and she wants her daughter Olivia kept out of trouble with the law – which is not easy for Peter to deliver. Peter's involvement soon grows deeper when an autopsy by pathologists who know about magic reveals that the dead girl, Christina Chorley, had died not only of a drug overdose but also of a wild and excessive use of magic – which can cause a careless practitioner's brain to undergo hyperthaumaturgical degradation, with often fatal results. Peter plunges into the investigation, in partnership with the Muslim policewoman Sahra Guleed – who has no training in magic but makes up for it in her courage and dedication. It is far from easy, since it is needed to interview various very rich and influential people, who resent the police digging into their affairs and who use their connections in the Metropolitan Police's command structure to obstruct the investigation. To further confuse the issue, there come up traces of a long-lost manuscript by Isaac Newton, who secretly founded modern magic. This lost Third Principia, stolen by the 18th Century master criminal Jonathan Wild, supposedly deals with alchemy, the Philosopher's Stone and possibly even with how to attain eternal life. Various magically-inclined individuals and groups are involved in the hunt for this treasure:
Viscountess Helena Linden-Limmer, heiress to a long line of witches and sorceresses who disdain male-dominated magic, and her daughter Caroline who aspires to learn how to fly magically without wings or mechanical aids
A bunch of American wizards known as the Virginia Gentlemen, with links to the US intelligence community – who bungled badly when using magic at Falluja during the Iraq War, but are now intensively active in London
The various not-quite-human beings known collectively as The Demi-monde, identifying themselves as fae and strongly objecting to being called goblins. Their favourite gathering place is the sinister Chestnut Tree Pub, built around the still-existent Tyburn Tree, on which London criminals used to be hanged
In particular, a specific denizen of this Demi-monde known as Reynard Fossman, a highly enterprising and competent criminal rumoured to be in possession of the secret Newton manuscript
Sir William Tyburn – an earlier deity of the River Tyburn. Considered to have been killed by the river's industrial pollution in the 19th Century, he suddenly re-appears – using a 14th Century broadsword to kill a 21st Century underworld hired killer. On another occasion, he is seen at night running across the parks of modern London, painted blue with woad and stalking mysterious prey with spears
All of these and more are constantly running into each other, ruining each other's plans but sometimes inadvertently saving each other's lives. Gradually, however, other issues become side-lined as Peter Grant and his mentor, the veteran wizard Nightingale, find themselves heading for an explosive showdown with their arch-enemy – the very powerful and utterly ruthless wizard known as The Faceless Man. Also involved is the renegade policewoman Leslie May – once Peter Grant's valued colleague with whom he was deeply in love, now The Faceless Man's cunning and highly resourceful accomplice.
The titanic magical battle thoroughly wreaks the luxurious apartment building where everything began. "He almost got me, you know" Nightingale recounts afterwards. "He's prepared a number of booby traps and tried to lure me into the killing zone". However, though the Faceless Man is clever and ruthless, he lacks combat experience, while Nightingale is a veteran of deadly battles against Nazi German wizards in the Second World War – enabling him to survive all traps and relentlessly pursue his foe. Meanwhile, Peter and Leslie engage in intensive magical duels of their own – but remember enough of their past to still make an effort not to kill each other. In the event, no one is killed. The Faceless Man and Leslie make good their escape, to fight again another day. However, he is The Faceless Man no longer. His true name and antecedents had been revealed, and a wealth of information gained on his background and motivations: an upper-class English Nationalist, a racist who romanticizes the Dark Ages and admires Alfred the Great and dreams of the English once again ruling the world. In the aftermath, Newton's famed Third Principia had fallen into the hands of Lady Helena Linden-Limmer – and Nightingale is content to leave her the task of deciphering its obscure Latin. Peter goes back to his idyllic relationship with the delightful Beverly, doing some needed work on improving her eponymous Beverley Brook. However, Lady Ty invites him to a stern talk, to warn of the dangers and dilemmas inherent in a mortal man loving an immortal goddess.
Critical opinion
Stephenie Sheung on The Speculative Herald wrote: "After two years of watching the release date hover in flux and getting pushed back time and time again, I must confess waiting for this book was its own special kind of agony. That was also when I realized I was irrevocably addicted to Peter Grant. It fell short of being one of the bestPeter Grant books because it had a lot less of the dry, sardonic humor which has always been one of the key hallmarks of this series. While still very enjoyable, this might be the first one that didn’t make me literally laugh out loud. There also wasn’t enough of Nightingale. What I wouldn’t give to see him kick some ass again in another epic wizarding duel, instead of just hearing everyone around him talk about it. In terms of criticisms though, that was probably the extent of it, which made me very happy since I had such high expectations for this book. It wasn’t always fast-paced, but as far as police procedurals go, it had just the right amount of mystery, suspense, and action. The story had so many moving parts that Aaronovitch was constantly juggling and keeping aloft, I can’t say there was really much time for anything else. Still, we got to see a little more of Peter’s relationship with Beverly, and I’m also enjoying the larger role of Sahra Guleed, another police officer who is shaping up to be the perfect partner for Peter while the two of them are on the beat. This book is what I would call a real game-changer. While it did end rather abruptly, it’s clear that Peter and the gang will have to tread even more carefully going forward, and the next book should be very interesting indeed. Now if I can only survive the wait…"
