When the body of an MI5 operative is found floating in the Thames, police frogmen find a significant clue nearby: Nikolai Sereyev, an MI5 informer and mid-level player in a Russian criminal organisation. Both men have been brutally murdered. Andrew Harvey is tasked with finding his colleague's killer, and quickly uncovers a plot to assassinate a visiting dignitary on British soil. No sooner has he scraped the surface of the case than the tables are...