London 1699. The Countess Anastasia Ashby de la Zouche, Baroness Penge, Countess Clapham, former mistress to Charles II, has fallen on hard times.
In order to scrape a living, she embarks on a career gathering salacious information for one of London's scandal sheets, assisted by her ex-maidservant Alpiew. They are approached by a stranger who wants them to follow her husband, Beau, for proof of adultery. The uncomfortable job of trailing after the handsome merchant in the depths of winter ends abruptly in a Convent Garden churchyard.
The countess and Alpiew, now implicated in a murder, get sucked into a complex labyrinth of deceit and violence, the key to which might lie in the abstruse science of alchemy. The more they investigate, the more convoluted the picture becomes, involving everyone from the lowest of low backstreet criminals to some of the most influential people in the land.
