1665, and the Great Plague has London in its grip. Everyone who can has fled and the only sounds are the tolling bells and the incessant cry of 'bring out your dead!'. Where better, then, to hide a murdered man than amongst the corpses on their way to the plague pit?

John Grey, now a successful lawyer, is called in by Secretary of State Lord Arlington to investigate an unexpected admission to the Tothill pit. The man was, before his murder, known to be carrying a letter from the Duke of York to the French ambassador. But the letter has vanished and Arlington wants it.

Grey soon begins to realise why Arlington is prepared to pay well for the document. The contents will compromise not only the duke but many others around him. But Arlington is not the only one trying to recover the letter. Somebody has killed once to try to obtain it - and is prepared to kill again. And Samuel Pepys's offer of help may not be all it seems. So John Grey is forced to set off on a journey through plague-ravaged England to fulfil his commission and keep himself safe from his enemies - if the Plague doesn't get him first.