Murder on the Dubai Express

Just a thought:

"Poirot's second explanation is rather more sensational: All of the suspects are guilty. Poirot's suspicions were first piqued by the fact that these people were acquaintances of many different European nationalities. Poirot reasons that this usually occurs in the United States of America, the "melting pot" where a Scotsman may be acquainted with an Italian and a German, all of different social classes and all at the same time. There was no other way the murder could have taken place, given the evidence. Poirot reveals that the other passengers were all relatives, servants, or friends of the Armstrong family, or had connections to the crime. All had been gravely affected by Daisy's murder and the consequences of the crime. They took it into their own hands to serve as Cassetti's executioners, to avenge a crime the law was unable to punish. Each of the suspects stabbed Ratchett once, so that no one could know who delivered the fatal blow. Twelve of the conspirators participated to allow for a "twelve-person jury", with Count Andrenyi acting for his wife, as she (Daisy's aunt) would have been the most likely suspect. One extra berth was booked under a fictitious name - Harris - so no one but the conspirators and the victim would be on board. (The cabin next to Ratchett was already reserved for a director of the Wagons-Lits.)"