Murder on the Orient Express (1934) - A murder mystery starring Hercule Poirot - a complex mystery

By the time that this book was published (in 1934), Hercule Poirot had a big fan base and people would wait for a new novel to be released by Agatha Christie. The book is extremely famous, and has also been converted into a movie. The base plot of the book is seemingly based on the Lindberg baby kidnapping where the baby son of the famous aviator Charles Lindberg was kidnapped. Tragically, the child was murdered, and this was a very famous case (since Lindberg was extremely famous after doing a solo flight across the Atlantic). And the book has a similar case, where the person who was murdered was revealed to be behind a similar crime, something that gets revealed during the course of the investigation of the murder. The ending is a bit surprising for those who have read many of the other Hercule Poirot novels (and just for that, in this review, I will not reveal the ending - so if you have not read the book, try and get it).
Hercule Poriot is returning from Syria in the Orient Express in Istanbul, and has had to take help from a friend who is a director on the train company Compagnie Internationale des Wagons-Lits; he gets a berth when another traveler fails to show up.



And like many other mysteries, Poirot just happens to be on the scene when a murder happens (something which scares the perpetrators of the crime, since in the normal course of things, this would not have been a crime that would have been easily solved). In the course of a night near Belgrade, Poirot seems to hear a sound outside his door more than once, and does not encounter anybody. Further, a lady Mrs. Hubbard seems to believe that somebody was in her apartment. However, nobody is to be found.
The next morning, they find one of the passengers, Mr. Ratchett, to have died, rather been murdered. He was killed by many stab wounds, some from left handers, some from right handers, and some much deeper than the others. The train is stuck in a snow-storm, so it would seem that the murdered is still on the train. Poirot is the only one who can investigate, and he starts his investigation. He finds a number of clues, but many of them point in different directions. And then he discovers the past of Mr. Ratchett, who was actually a fugitive from the US called Cassetti. And he was behind the kidnap and murder of a young heiress, Daisy Armstrong, and had then fled from the country. Her parents died from the shock (her mother died from the shock, and her father killed himself).
And as he investigates, he realizes that other passengers on the train all had connections to the Armstrong family in the past, and thus any of them could have a motive, so who was the actual killer ?