Poirot opens the Court of Inquiry in the dining car of the train. He calls in Pierre Michel, conductor of the Wagon Lit. Pierre Michel is a Frenchman that has been employed with the company for over fifteen years and is considered quite trustworthy and honest. Pierre recounts his actions the previous evening for Poirot. He tells Poirot that Ratchett asked for his made up while he was at dinner so he could retire early. Hector McQueen was seen entering his compartment sometime afterward. At 12:40 in the morning Ratchett rang the, but when the Conductor came to his door Ratchett told him he had made a mistake. After responding to Ratchett, Pierre went to the Athens coach to visit a colleague, but was called back sometime after one in the morning by Mrs. Hubbard's bell and then Poirot's bell. A half an hour later the Conductor made up McQueen's bed. McQueen had been up talking with Colonel Arbuthnot. The Conductor did not see any other movement in the hallway except for a lady with a scarlet kimono with dragons on it. The Conductor also informs Poirot that the train has been well searched and there is no assassin hiding on board, the last stop on the train was at Vincovci at 11:58 where he descended from the train with the other conductors.
Poirot calls Hector McQueen for a second interview. Poirot divulges Ratchett's real name and crime. McQueen seems very surprised and tells Poirot he would have never worked for Ratchett had he known his true identity. McQueen's father was the district attorney who handled the Armstrong case and McQueen felt great sympathy for the family. McQueen tells Poirot that after dinner he returned to his compartment and read a bit. At Belgrade, McQueen fell into conversation with Colonel Arbuthnot. The gentlemen ended up talking about politics until 2AM in McQueen's compartment and then McQueen fell asleep. At Vincovci he and Arbuthnot both got out of the train to stretch. The only person McQueen noticed in the hallway was a woman with a scarlet silk robe passing his door. McQueen never saw the unidentified lady return.
Poirot brings M. Ratchett's valet, Edward Henry Masterman, in for questioning. The valet explains he last saw Ratchett at approximately 9PM. The valet went to Ratchett's room to fold his clothes, put his dental plate in water and gave him his sleeping draught. Ratchett seemed to be upset and on edge, everything the valet did upset him. Ratchett told Masterman he did not want to be disturbed until he rang the next morning. Masterman was not surprised that he didn't call the next morning right off because Ratchett often didn't rise till lunchtime. After leaving Ratchett, Masterman told McQueen Ratchett wanted him and went to his own compartment and read. Masterman shares the No. four compartment with the Italian. He read until 10:30, when the conductor came and made up the beds for the night, but did not drift off until four in the morning because of a bad toothache. He knew Ratchett had certain enemies because he had heard conversations between Ratchett and McQueen discussing some of the threatening letters. Masterman had no knowledge of Ratchett's real identity, but told Poirot he was familiar with the Armstrong case. Masterman is a cigarette smoker.
Part 2 begins with Poirot's evidence gathering. Prior to the interviews he takes in these chapters, Poirot does find evidence in Ratchett's compartment—most notably the charred piece of paper with the Daisy Armstrong's name on it and the curious nature of the stab wounds, but in Section two Poirot formally begins to collect evidence for the crime. Murder on the Orient Express, as many of Christie's novels, are extremely formulaic; however, Christie is no exception—most all detective and mystery fiction have a "set" formula: one) a statement of problem, two) production of data for solution and three) the discovery. Writers have, of course, debated and stretched these rules, but Christie stunningly adheres to them in the Murder on The Orient Express. She even divides her sections accordingly: "The Facts," "The Evidence," "Hercule Poirot Sits Back and Thinks."
Christie has often been criticized for this adherence to the tenets or rules of detective fiction. As Georges Simeonon's remark goes about Christie's books, "It's not literature, it's embroidery"—there is a tight underlying pattern in her stories. Francis Wyndham characterized Christie's work as "animated algebra": "Agatha Christie writes animated algebra. She dares us to solve a basic equation buried beneath a proliferation of irrelevancies." Murder mysteries have been compared to mathematical equations, games and Shakespearian sonnets because they fall into strict patterns. These patterns sometimes exclude them from serious literary analysis because the authors tend not to deviate far from the set patterns. Several authors have even established set of rules for detective fiction in an attempt to define the genre. Needless to say, these rules are often broken. What does seem clear and consistent between detective novels, certainly Christie's, is the idea of game. There is a challenge implicit in reading any detective book. There is a challenge between the detective and the reader and the writer and the reader—a battle of wits to see who can figure out the murderer first. The nature of detective fiction is to "sanitize" the relationship between the murderer and the victim to allow for the challenge between writer and reader. The "embroidery" described by Simieons, a critic who was not terribly fond of Christie's writing, is her genius. The intricacy of diversion and careful layering of her stories heighten the challenge to uncover the solution before Poirot.
Up to the last chapters, the reader is comfortable with the book's format, and the novel progresses as expected. Poirot finds the body in the beginning of the book, works to gather evidence and finally discovers who the murders are. What is unexpected in Murder on The Orient Express, the rule Christie herself toyed with, is the fact that there is a whole train full of murderers. People will assume that there might be one or two murderers, but a whole bunch, an exceptional family like the Armstrongs, is quite out of the ordinary. The surprise ending is a surprise because is goes against the formula of who a murderer or murderers should be. Christie uses the conventions of a detective novel against the reader.