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 young man in a brown suit is identified as a suspect, having entered the house soon after.