What to read after The Man in the Brown Suit?

Nadina, a dancer in Paris, receives a visit from Count Sergius Paulovitch. Both are in the service of "the Colonel", an international agent provocateur and criminal. "The Colonel" is retiring, leaving his agents high and dry. Nadina has a plan to blackmail the Colonel. Anne Beddingfeld is an orphan after the sudden death of her archaeologist father. Longing for adventure, she jumps at the chance live in London. Returning from an unsuccessful job interview, Anne is 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. Anne picks up the note he dropped, which reads "17.1 22 Kilmorden Castle". The inquest of L B Carton brings a verdict of accidental death. Carton carried a house agent's order to view Mill House in Marlow, and the next day the newspapers report that a dead woman has been found there, strangled. The house belongs to Sir Eustace Pedler MP. A young man in a brown suit is identified as a suspect, having entered the house soon after the dead woman.