The Man in the Brown Suit
Orphan Anne Beddingfeld, in search of adventure, follows the clue in a note from the pocket of a murder victim. Her journey takes her on an ocean voyage from London to Africa, and finally to a lost island, on the trail of stolen diamonds. Nadina, a "Russian" dancer, receives a visit in her dressing room from Count Sergius Paulovitch. Both are in the service of a man they call "the Colonel", an international agent provocateur and criminal. After many years, "the Colonel" is retiring, leaving his agents high and dry. Nadina has double-crossed the Colonel, however, keeping some De Beers diamonds from a crime years before. She now plans to blackmail the Colonel with the diamonds.
Anne, longing for adventure, jumps at the chance offered by her father's solicitor to live with him and his wife in London. Returning from an unsuccessful job interview, 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 inquest on the dead man, "L B Carton", brings a verdict of accidental death. In his pocket was a house agent's order to view a house for let – The Mill House in Marlow – and the next day the newspapers report that a dead woman has been found there, strangled. The house is owned by 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.
Anne realises the 'doctor' did not examine the dead man in an appropriate manner, and becomes suspicious. After fruitless investigations at Mill House, where she finds an undeveloped canister of film, Anne discovers that Kilmorden Castle is the name of a ship sailing on 17 January 1922 from Southampton to Cape Town. She books passage on it. On board the ship, Anne meets Suzanne Blair, Colonel Race, and Sir Eustace Pedler himself. In addition to his normal secretary, Guy Pagett, he has employed a man who goes by the name of Harry Rayburn. At 1:00 am on the morning of the 22nd, a young man staggers into Anne's cabin having been stabbed. Anne is able to dress the man's slight wound but the man is not in the least bit grateful and leaves after an altercation with her.
One evening on the ship, Colonel Race recounts the story of the theft of a hundred thousand pounds' worth of diamonds some years before, supposedly by the son of a South African gold magnate, John Eardsley, and his friend Harry Lucas. John and his friend were arrested but John's father, Sir Laurence, disowned his son. John Eardsley was killed in the war and his father's huge fortune passed to his next of kin. Lucas was posted as "missing in action". Harry Rayburn walks into the cabin as the story is being told, overhears it, looks sick, and leaves. Race reveals that he himself is the fortunate next of kin.
Anne confides in Suzanne and they examine the piece of paper Anne obtained in the Underground station. They realise that the paper could refer to cabin 71 – Suzanne's cabin, originally booked by a Mrs Grey, a pseudonym for Nadina. Anne and Suzanne speculate that Nadina was the dead woman in the Mill House. Anne suddenly connects finding the film roll in Mill House with a canister of film that was dropped into Suzanne's cabin on the night of the 22nd. They look inside the canister and find uncut diamonds. They speculate that Harry Rayburn is the "Man in the Brown Suit". Anne is attacked as she walks the deck of the ship; Harry Rayburn saves her. Anne amazes Harry with her knowledge of events in Marlow and at Hyde Park Corner station, and suggests that Harry may be Harry Lucas and the "Man in the Brown Suit". They again part on bad terms.
Once they arrive in Cape Town, Anne is lured to a house at Muizenberg, where she is imprisoned in the attic by a bearded Dutchman. Anne overhears another person she met on board the Kilmorden Castle, the Rev. Chichester, speaking with the Dutchman about "the Colonel" wanting to question her tomorrow. The next day she escapes and makes her way back to Cape Town. There she finds that Harry is wanted as the "Man in the Brown Suit" but has gone missing. Pedler offers Anne the role of his secretary on his continuing trip to Rhodesia; she accepts at the last second, and is reunited on the train with Race, Suzanne, and Pedler, who has another new secretary named Miss Pettigrew.
In Bulawayo, Anne receives a note from Harry which lures her out to a ravine near their hotel. There she is chased and falls into the ravine. Almost a month later, Anne awakens in a hut on an island in the Zambezi with Harry Rayburn, who rescued her. He reveals that someone deliberately caused her to fall. Anne and Harry fall in love. Harry tells her of the diamond discovery he and John Eardsley made years earlier. They were duped by a young woman called Anita Grünberg, who substituted their diamonds for ones stolen from De Beers. After being listed as missing in action, Harry disappeared, coming to Africa under the name of Harry Parker.
Some time later he came across a man – Carton – and recognised him from the incident with Anita Grünberg. Carton is revealed to be the man who fell in the Tube station and dropped the note Anne found. Harry followed Carton to London and Nadina to the Mill House, but insists Nadina was already dead. He realised that the diamonds were probably still on the Kilmorden Castle. Anne confirms that they were, and were handed to Suzanne in her cabin on the night of the 22nd. Harry's island is attacked that night by a party led by the red-bearded Dutchman, but the two manage to escape, and Anne plans to return to Pedler's party where she can keep an eye on developments. They exchange codes to be used in future communications so that neither can be duped again. Reunited with Suzanne, Anne is told that the diamonds are with luggage sent on with Sir Eustace. She also receives a telegram from Harry telling her to meet him.
Anne goes to the meeting with Harry and again bumps into Chichester, alias Miss Pettigrew. She is led to Sir Eustace, alias "the Colonel". Pedler forces Anne to write a note to Harry to lure him to his office, which she does, but she does not include their code in it. Harry turns up and Pedler is exultant – until Anne pulls out a pistol and they capture Pedler. Race turns up with reinforcements and Pedler tries to bluff matters out, but is unsuccessful. Sir Eustace manages to escape. Anne is somewhat pleased, having developed a fondness for him. Race tells her that Harry is in fact John Eardsley, not Harry Lucas, and therefore the heir to the fortune. Harry however has found his happiness with Anne, and they marry and live on the island in the Zambezi.
murder, flashback