Its really long but extremely precise.you can't break a novel of over 100pages into a few lines.
Returning from an important case in Syria, Hercule Poirot boards the Orient Express in Istanbul. The train is unusually crowded for the time of year and Poirot is able to secure a place only with the help of his friend Monsieur Bouc, a director of the company which operates the Express. When a Mr. Harris fails to show up, Poirot takes his place, to the surprise of his roommate Mr. McQueen. However, on the second night, Poirot gets a compartment to himself.
On the second night out from Istanbul, at about twenty-three minutes before 1:00 am, Poirot wakes to the sound of a loud noise. It seems to come from the compartment next to his, which is occupied by Mr. Ratchett. When Poirot peeks out his door, he sees the conductor knock on Mr. Ratchett's door and ask if he is all right. Mr. Ratchett replies in French that he is fine, and the conductor moves on to answer a bell down the passage. Poirot decides to go back to bed but he is disturbed by the fact that the train is unusually still and his mouth is dry. As he lies awake, he hears Mrs. Hubbard ringing the bell urgently. When Poirot then rings the conductor for a glass of water, he learns that Mrs. Hubbard was afraid that someone had been in her compartment. He also learns that the train has stopped due to a snowstorm. Poirot dismisses the conductor and tries to go back to sleep, only to be wakened again by a thump on his door. This time when Poirot gets up and looks out of his compartment, the passage is completely silent, and he sees nothing except the back of a woman in a scarlet kimono retreating down the passage in the distance.
The next day he awakens to find that Mr. Ratchett is dead, having been stabbed twelve times in his sleep. However, the clues and circumstances are very mysterious. Some of the stab wounds are very deep and some are glancing blows. Furthermore, some of them appear to have been inflicted by a right-handed person and some by a left-handed person.
Poirot finds several more clues in the victim's cabin and on board the coach, including a linen handkerchief with the letter "H" on it, a pipe cleaner, and a button from a conductor's uniform. All of these clues suggest that the murderer or murderers were somewhat sloppy. However, each clue seemingly points to different suspects, which suggests that some of the clues were planted.
By reconstructing some bits of a burned letter, Poirot soon discovers that Mr. Ratchett was a notorious fugitive from the U.S. named Cassetti. Some years earlier, Cassetti kidnapped three-year-old heiress Daisy Armstrong. Though the Armstrong family paid a large ransom for Daisy's release, Cassetti murdered the little girl regardless and fled the country with the money. Daisy's mother, Sonia Armstrong, was pregnant when she heard of Daisy's death. The shock sent her into premature labor, and both she and the child died. Her husband, Colonel Armstrong, shot himself out of grief. Mrs. Armstrong's maid, Susanne, was suspected by the police, despite her protests. She threw herself out of a window of the Armstrong house and died after which she was proved innocent.
As the evidence mounts, it continues to point in wildly different directions and it appears that Poirot is being challenged by a master mind. A critical piece of missing evidence - the scarlet kimono worn the night of the murder by an unknown woman — turns up in Poirot's own luggage.
Poirot discovers that some of the passengers had connections to the victim, while others had connections to the Armstrong family.
MacQueen's father was the police official in charge of the Armstrong case.
Masterman was Colonel Armstrong's batman during the war and his valet in New York.
Pierre Michel was the father of Suzanne, the maid driven to her death.
Miss Debenham was Mrs.Armstrong's secretary & Countess Andrenyi's governess.
Colonel Arbuthnot was Colonel Armstrong's brother officer and best friend.
Princess Dragomiroff was Mrs. Armstrong's godmother.
Countess Andrenyi was Mrs. Armstrong's sister.
Count Andrenyi was Mrs. Armstrong's brother-in-law.
Miss Schmidt was the Armstrong family's cook.
Mrs. Hubbard was Mrs. Armstrong's mother.
Foscarelli was the Armstrong family's chauffeur.
Hardman was a private detective who fell in love with Susanne.
Greta Ohlsson was Daisy's nurse.
After meditating on the evidence for some time, Poirot assembles the thirteen suspects, plus M. Bouc and Dr. Constantine, in the restaurant car where he lays out two possible explanations of Ratchett's murder.
Poirot's first explanation is that a stranger entered the train during the previous stop at Vincovci, murdered Ratchett for reasons unknown, and escaped unnoticed. The crime occurred an hour earlier than everyone thought, because the victim and several others failed to note that the train had just crossed into a different time zone. The other noises heard by Poirot on the coach that evening were unrelated to the murder. However, Dr. Constantine says that Poirot must surely be aware that this explanation does not fully explain the circumstances of the case.
Poirot's second explanation is rather more sensational: all of the suspects are guilty. Poirot's suspicions are first piqued by the fact that each of these individuals are acquaintances of different European nationalities and/or ethnicities. Poirot reasons that this usually occurs with those who are connected to the United States of America, the “melting pot” where a Scotsman, may also be an acquaintance of 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 in fact 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 only Countess Andrenyi not participating, as she (Daisy's aunt) would have been the most likely suspect. One extra berth was booked under a fictitious name (the cabin next to Ratchett was already reserved for a director of the company) so no one other than the conspirators and the victim would be on the train that night. The unexpected stoppage in the snowbank, and the fact that the carriage company had allowed the famous Poirot to take the cabin reserved for the fictitious person, caused complications to the conspirators that resulted in several crucial clues being left behind. As Poirot reveals the details of the elaborate plot, many of the suspects (among them Daisy's aunt and grandmother) break down in tears.
Poirot agrees to let Dr. Constantine and M. Bouc decide which of his two theories is correct. After a brief pause, both state softly that the first explanation seems far the more plausible, and is the one they will give to the police when the freed train reaches the next station. His task completed, Poirot retires from the case, admitting that, albeit glad to see justice served, the case initiated "a struggle with [his] conscience".