The man in the brown suit

Anne is on the platform at Hyde Park Corner tube station when a man falls onto the live track, dying instantly. A doctor examines the man, pronounces him dead, and leaves, dropping a note on his way. Anne picks up the note, which reads "17.1 22 Kilmorden Castle". The next day the newspapers report that a dead woman has been found there-- strangled. Anne becomes involved in a world of diamond thieves, murderers and political intrigue.