A serial killer stalks the agents of Department Z in a rip-roaring thriller from the Edgar Award-winning author who sold eighty million books worldwide.   London, 1941. In the unending darkness of the London Blackout, an assassin slinks through the night, striking down victims with deadly accuracy. His targets are agents, killed while on watch.   Department Z is baffled. Who is the silent killer, why is he targeting them, and what is their secret . . . just how are they managing to take down the best-trained agents in Britain?   Gordon Craigie, Department Z's fearless leader, soon finds himself faced with the toughest challenge of his career--to catch the killer before his deadly skill falls into enemy hands, putting all of Europe in grave danger . . .   "Mr. Creasey realizes that it is the principal business of thrillers to thrill." --Church Times   "Little appears in the newspapers about the Secret Service, but that little makes anything on the subject probable fiction. Mr. Creasey proves himself worthy of the chance." --The Times Literary Supplement