July 1794, and the streets of London are filled with rumours of revolution. Political radical Thomas Hardy is to go on trial for treason, the war against the French is not going in Britain's favour, and negotiations with the independent American colonies are on a knife edge. Laurence Jago - clerk to the Foreign Office - is ever more reliant on the Black Drop to ease his nightmares. A highly sensitive letter has been leaked to the press, which may lead to the destruction of the British Army, and Laurence is a suspect. Then he discovers the body of a fellow clerk, supposedly a suicide. Blame for the leak is shifted to the dead man, but even as the body is taken to the anatomists, Laurence is certain both of his friend's innocence, and that he was murdered.