Former intelligence agent Serafina Montserrat believes that an old European conspiracy is active again, but age and failing memory make her warning difficult to assess. Thomas Pitt must decide whether she possesses genuine knowledge of a threat to the crown or is being manipulated by someone who wants Special Branch diverted.
As a visiting Austrian royal approaches London, Pitt, Charlotte and Victor Narraway investigate the people around Serafina and the secrets of her earlier work. The case links private vulnerability to an assassination scheme whose success could alter European politics.