London, 1785. When the body of a West Indies planter is found pegged out in the grounds of St Paul's Cathedral, suspicion falls on one of the victim's former slaves, who was found with his watch on the London streets. But it seems the answer is not that simple. The impact of the planter's death brings tragedy for Francis Glass, a freed slave now working as a bookseller and printer in the city, and a painful reminder of the past for William Geddings, Harriet Westerman's senior footman. Harriet is reluctant to be drawn in to the difficult and powerful world of the slave trade, but she and her friend, reclusive anatomist Gabriel Crowther, begin to understand the dark secrets hidden by the respectable reputation of London's slave owners. Together, they negotiate the interests of the British government, the secrets of the plantation owners, and a network of alliances stretching across the Atlantic. And they must confront the uncomfortable truth that some people are willing to do great evil when they believe their cause to be just.