The Mystery of the Blue Train

Poirot boards Le Train Bleu, bound for the French Riviera. So does Katherine Grey, who is having her first winter out of England, after recently receiving a relatively large inheritance. On board the train Grey meets Ruth Kettering, an American heiress leaving her unhappy marriage to meet her lover. The next morning, though, Ruth is found dead in her compartment, a victim of strangulation. The famous ruby, "Heart of Fire", which had recently been given to Ruth by her father, is discovered to be missing. Ruth's father, the American millionaire Rufus Van Aldin, and his secretary, Major Knighton, persuade Poirot to take on the case. Ruth's maid, Ada Mason, says that she saw a man in Ruth's compartment but could not see who he was. The police suspect that Ruth's lover, the Comte de la Roche, killed her and stole the ruby, but Poirot does not think that the Comte is guilty. He is suspicious of Ruth's husband, Derek Kettering, who was on the same train but claims not to have seen Ruth. Katherine says that she saw Derek enter Ruth's compartment. Further suspicion is thrown on Derek when a cigarette case with the letter "K" is found there.

Poirot investigates and finds out that the murder and the jewel theft might not be connected, as the famous jewel thief The Marquis is connected to the crime. Eventually, the dancer Mirelle, who was on the train with Derek, tells Poirot she saw Derek leave Ruth's compartment around the time the murder would have taken place. Derek is then arrested. Everyone is convinced the case is solved, but Poirot is not sure. He does more investigating and learns more information, talking to his friends and to Katherine, eventually coming to the truth. He asks Van Aldin and Knighton to come with him on the Blue Train to recreate the murder. He tells them that Ada Mason is really Kitty Kidd, a renowned male impersonator and actress. Katherine saw what she thought was a boy getting off the train, but it was really Mason. Poirot realised that Mason was the only person who saw anyone with Ruth in the compartment, so this could have been a lie. He reveals that the murderer and Mason's accomplice is Knighton, who is really The Marquis. He also says that the cigarette case with the K on it does not stand for 'Kettering', but for 'Knighton'. Since Knighton was supposedly in Paris, no one would have suspected him. Derek did go into the compartment to talk to Ruth once he saw she was on the train, but he left when he saw she was asleep. The police then arrest Knighton and the case is closed.

• Hercule Poirot
• Rufus Van Aldin, the American millionaire, Ruth’s father
• Ruth Kettering, Van Aldin’s only daughter, Derek’s wife
• Derek Kettering, Van Aldin’s son-in-law, Ruth’s husband
• Ada Mason, Ruth Kettering's maid
• Armand the Comte de la Roche
• Monsieur Carrege, of French police
• Commissary Caux, of French police
• Charles Evans (a.k.a. Chubby), Lady Tamplin’s younger husband
• Mr. Goby, Rufus’s informant
• Mr. and Mrs. Harrison, Katherine’s good friends in the village
• Joseph Aarons, Poirot’s acquaintance, an expert in people with “dramatic profession”
• Katherine Grey, an ex-companion to Mrs. Harfield, to whom the other’s wealth is left in her will
• Major Richard Knighton, Van Aldin’s secretary
• Hon. Lenox Tamplin, Lady Tamplin's daughter
• Mirelle, a Parisian dancer, Derek’s lover
• M. Papopolous, the jewellery dealer, an acquaintance of Poirot’s
• Lady Rosalie Tamplin, Lenox’s mother, a cousin of Katherine’s; with whom she stays in her villa
• Pierre Michel, the train’s attendant[5]

The novel's plot is based on the 1923 Poirot short story "The Plymouth Express" (later collected in book form in the US in 1951 in The Under Dog and Other Stories and in the UK in 1974 in Poirot's Early Cases).

This novel features the first mention of the fictional village of St. Mary Mead, which would later be the home of Christie's detective Miss Marple. It also features the first appearance of the minor recurring character, Mr Goby, who would later appear in After the Funeral and Third Girl. The book also features the first appearance of Poirot's valet, George.

Mere months after this novel was published, prolific French novelist Arthur Bernède published "Le mystère du train bleu"[6] in late 1928. A murder mystery adventure featuring Bernède's own popular detective, Chantecoq, the story is set in Paris and the plot is completely different. It seems likely, however, that Bernède was hoping to benefit from Poirot's popularity.

The Times Literary Supplement gave a more positive reaction to the book than Christie herself in its issue of 3 May 1928. After recounting the set-up of the story the reviewer concluded: "The reader will not be disappointed when the distinguished Belgian on psychological grounds declines to suspect the arrested husband and, by acting on the suggestion of an ugly girl who consistently derides her preposterous mother, builds up inferences almost out of the air, supports them by a masterly array of negative evidence and lands his fish to the surprise of everyone".[7]

The New York Times Book Review of 12 August 1928 said, "Nominally Poirot has retired, but retirement means no more to him than it does to a prima donna. Let a good murder mystery come within his ken, and he just can't be kept out of it."[8]

British crime writer and critic Robert Barnard declared: "Christie's least favourite story, which she struggled with just before and after the disappearance. The international setting makes for a good varied read, but there is a plethora of sixth-form schoolgirl French and some deleterious influences from the thrillers. There are several fruitier candidates for the title of 'worst Christie'."[9]

One of the characters in Death on the Nile recognises Poirot because of his involvement in The Mystery of the Blue Train: "Miss Van Schuyler said: ' I have only just realised who you are, Monsieur Poirot. I may tell you that I have heard of you from my old friend Rufus Van Aldin." That line was retained in the television film, even though Death on the Nile was broadcast first.

The titular Blue Train appears again in Three Act Tragedy where Poirot boards the train with Sir Charles Cartwright to return to England.

• 1928, William Collins and Sons (London), 29 March 1928, Hardcover, 296 pp
• 1928, Dodd Mead and Company (New York), 1928, Hardcover, 306 pp
• 1932, William Collins and Sons, February 1932 (As part of the Agatha Christie Omnibus of Crime along with The Murder of Roger Ackroyd, The Seven Dials Mystery and The Sittaford Mystery), Hardcover (Priced at seven shillings and sixpence)
• 1940, Pocket Books (New York), Paperback, 276 pp
• 1948, Penguin Books, Paperback, (Penguin number 691), 250 pp
• 1954, Pan Books, Paperback (Pan number 284)
• 1956, Pocket Books (New York), Paperback, 194 pp
• 1958, Fontana Books (Imprint of HarperCollins), Paperback, 248 pp
• 1972, Greenway edition of collected works (William Collins), Hardcover, 286 pp, ISBN 0-00-231524-6
• 1973, Greenway edition of collected works (Dodd Mead), Hardcover, 286 pp, ISBN 0-396-06817-0
• 1974, Dodd, Mead and Company (As part of the Murder on Board along with Death in the Clouds and What Mrs. McGillicuddy Saw!), Hardcover, 601 pp, ISBN 0-396-06992-4
• 1976, Ulverscroft Large-print Edition, Hardcover, 423pp, OCLC 2275078
• 2006, Easton Press, Hardcover/Leather, 278 pp
• 2007, Poirot Facsimile Edition (Facsimile of 1928 UK First Edition), HarperCollins, 5 March 2007, Hardback ISBN 0-00-723438-4

The writing of this book (part of which took place on the Canary Islands in early 1927)[11] was an ordeal for Christie. The events of 1926, with the death of her mother, her husband's infidelity, and her breakdown and ten-day disappearance, had left a deep psychological scar and, now separated from Archie Christie and in need of funds, she turned back to writing. The story did not come easily to her and she referred to this novel in her autobiography stating that she "always hated it".[12] Her biography recounts how the total number of words in the book were carefully tallied up, showing what an ordeal Christie found it to be.[13] It later had an effect on her in the midst of wartime when, nervous that at some future point she might be in need of funds and need a fallback, she wrote Sleeping Murder and locked it securely in a bank vault for future publication.[14] Curtain was written at the same time and similarly locked away, but publication of this latter book would not be possible until the end of her writing career, as it recounts the death of Poirot.

The Mystery of the Blue Train was first serialised in the London evening newspaper The Star in thirty-eight un-illustrated instalments from Wednesday 1 February to Thursday 15 March 1928. The entire first two chapters were omitted from the serialisation and it therefore contained only thirty-four chapters. There were slight amendments to the text, either to make sense of the openings of an instalment (e.g. changing "She then..." to "Katherine then..."), or omitting small sentences or words, especially in the opening instalment where several paragraphs were omitted. A reference to the continental Daily Mail at the start of chapter six (chapter eight in the book) was changed to "the newspaper" to avoid mentioning a competitor to The Star. Three chapters were given different names: chapter nine (eleven in the book) was called Something Good instead of Murder, chapter twenty-six (twenty-eight in the book) was called Poirot hedges instead of Poirot plays the Squirrel and chapter twenty-eight (chapter thirty in the book) was called Katherine's letters instead of Miss Viner gives judgement. The final chapter, called By the Sea in the book, was unnamed in the serialisation.

This is the only major work by Agatha Christie in which the UK first edition carries no copyright or publication date.

• The Mystery of the Blue Train at the official Agatha Christie website
• The Mystery of the Blue Train (2005) at IMDb
• The Mystery of the Blue Train Blog Agatha Christie read online big collection