In the peaceful towns and villages of England, Cleaner Bob is washing windows, and people are dying in sudden and unexpected circumstances. When it becomes clear that the victims have a common history as Russian defectors, foul play is suspected and a hunt begins to locate their assailant, the lethal poison that killed them, and the mole who is leaking their locations. In a race against time, only one man has the connections and experience to crack the case before more people perish. Charles Thoroughgood, former head of MI6, is enjoying retirement in the Oxfordshire hamlet he calls home when the call comes in. A man of duty, he agrees to take part in a mission that will lead him into the heart of enemy territory and threaten to undermine the very values he holds most dear.