The unthinkable has happened at London's Peculiar Crimes Unit. In the depths of winter, a member of staff has been found murdered, and everyone who works there is suddenly a suspect. But Arthur Bryant and John May, the eccentric elderly detectives who run London's strangest crime division, aren't on hand to solve the crime. They've ventured into the heart of the English countryside, only to become stranded on a desolate snowbound section of road....

"A mysterious stranger in outlandish Edwardian garb defaces a painting in the national Gallery. Then a guest at the exclusive Savoy Hotel is fatally bitten by what appears to be a marshland snake. An outbreak of increasingly bizarre crimes has hit London and fittingly come to the attention of the Peculiar Crimes Unit."

Returning to the Victoria Cross pub hours after witnessing the murder of a woman, Detective Arthur Bryant is stunned to discover that the pub itself has vanished and the street around it has mysteriously aged, and calls in the Peculiar Crimes Unit to track down a killer who is stalking London's oldest watering holes.

Arthur Bryant and John May--and their team of proud eccentrics in the Peculiar Crimes Unit--have been given only one week to hunt down a murderer they've already caught once, but who somehow escaped from a locked room and killed one of their best and brightest. Facing a shutdown, Bryant and May, men of opposite methods, learn that their nemesis, expertly disguised, has struck again-and now he is luring them down into the vast labyrinth of tunnels...