The unthinkable has happened at London's Peculiar Crimes Unit. In the bitter depths of winter, a key 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. As the blizzard worsens, Bryant & May attempt to solve the crime long distance using only their mobile phones. Unfortunately, their situation is about to get very much worse. Unknown to the stranded detectives, an obsessed killer has travelled from the Riviera to Dartmoor, and is stalking the stranded vehicles, searching for one particular victim, coming closer with each passing minute...As if it didn't have enough trouble, the Peculiar Crimes unit is about to receive a demanding royal visitor, and the Home Office is preparing to shut the PCU down when the visit inevitably goes wrong...Two murderers, two incapacitated detectives, just six hours to solve two crimes and save the unit. Armed only with their wits, woolly coats and a stack of dubious veal and ham pies, Bryant & May are bracing themselves for the strangest day they've ever spent, trapped inside the white corridor...