The final thrilling instalment in the Williamson Papers, set in a superbly drawn Victorian London.

Back in England after surviving the horrors of Cawnpore, John Williamson returns to his hometown. On looking up an old friend, he finds the man hasn't been heard of since his departure to London, the glamorous capital of the British Empire. Concerned for his friend's safety, Williamson follows him to the metropolis, where he has fallen into bad company and now dwells in the notorious rookery of Seven Dials. Worse still, the intelligence services are on his trail, convinced that something worse than petty criminality is occurring in the slum: that foreign subversives are at work there, with catastrophic designs on Britain herself.

Blackmailed into helping the investigation, can Williamson manage to save his friend from certain death – and survive himself, in a world that condemns him for his sexuality?