July, 1665. As the great plague rages rampant outside London's city walls, pestilence exerts an ever stronger grip on the population. But Harry Lytle is forced to venture into some of the most diseased parishes in search of a serial killer. A grisly death starts Harry off on the trail and it's not long before his familiar accomplice, Dowling the butcher, joins him on the case. Their master, Lord Arlington, tasks them with uncovering the name and motive of the murderer - but there will be plenty more deaths and scrapes for Harry before the name is revealed. And things take a turn for the worst when the victim's companions decide that Harry is the prime suspect ...