I had no idea that anyone was carrying on the same dirty little tricks after all this time. Now I do. But if I don't move faster, they'll get me, before I can get them.

How can a long dead traitor destroy the man who uncovered his crimes?

London Summer 1912. Busy with the pressures of work and new motherhood, Margaret Demeray wonders if she will ever be free to help Fox again. When she hears of an unlikely spy plot, she expects Fox to be incredulous, but something reminds him of a case from 1902, and he decides to investigate.

Just as they decide the allegation is nonsense, a young woman is found dead and evidence at the scene links Fox to her murder. If he has any hope of avoiding arrest, he and Margaret must work out the links to that earlier investigation, when a traitor in the Boer War drowned on Fox's watch.

Is there someone now seeking revenge? Or is someone using knowledge of it to cover up the selling of military secrets? With London crippled by a series of strikes, Margaret and Fox struggle to try discover the truth, but as the net closes in on Fox, Margaret finds herself fighting not just for her family's safety but for his reputation... and ultimately his life.

Exactly how far is Margaret prepared to go to protect him?