What makes Murder on the Orient Express’s iconic ending work so well

Agatha Christie, author of one of the best-selling books of all time, playwright behind the world’s longest-running play, Dame Commander of the Order of the British Empire, and all around queen of the murder mystery, is a legend for many reasons. Between becoming the best-selling novelist of all time and developing and codifying the tropes that would define her genre, Christie had time to craft one of the most iconic whodunit reveals in all of mystery writing. It’s showing in theaters now in the new movie adaptation of Murder on the Orient Express.

The murder solution in Orient is so elegant, neatly crafted and inevitable-feeling, and yet so surprising at the same time, that it has become a byword. It’s its own trope now: You can say, “It’s a Murder on the Orient Express-style reveal,” and it means something. Here’s why this particular whodunit works so well in the context of its genre.

To be clear: We will be discussing the ending in detail. If you don’t want to be spoiled on the ending of an 83-year-old book, please look away now.

Christie’s 66 detective novels tend to be structural marvels: perfectly plotted mysteries in which the reader is provided with a murder, an array of suspicious characters, and just enough information that in theory, it should be possible to solve the murder. (I myself have never solved a Christie mystery on first reading, even when I knew going in what the famous ending was. “Did I remember it wrong?” I always ask about halfway through — but I am extremely susceptible to misdirection.)

But over the course of 66 novels, even the most artful misdirection begins to wear thin. What makes Murder on the Orient Express work so well is that it lets the tropes of the genre do the misdirecting for it.

The premise of Orient is as follows: A man on a train is murdered. Everyone on his particular train car (12 people, plus Detective Hercule Poirot) had the opportunity to do it. All of them behave in more or less suspicious ways. And this particular man is so famously vile — he murdered a child in a much-publicized case — that anyone in the world might have had the motive to kill him.

The train has been snowed in, and the police cannot reach it. It falls to Poirot to catch the murderer before the train begins to move again and the murderer makes their escape.

But Poirot is puzzled by the murder. The victim was stabbed multiple times, always by the same weapon, but sometimes with great strength and sometimes weakly. Could there are have been two murderers, he wonders? Two partners in crime, working together to kill a man?

No, he concludes at the end: There weren’t two murderers. There were 12. Every single person on the train car collaborated to commit the murder. Every last suspect is the who that dunit.

As soon as Poirot makes the reveal, the pieces fall neatly into place: Of course all 12 of them did it. Every last one of them was suspicious! And there’s even a clue hidden in plain sight: One of them informs Poirot that he believes deeply in “trial by jury,” and a jury requires 12 members — so every one of the murderers on the train is a member of the ad hoc “jury” that executes the victim.

But for most readers, the idea that everyone might have done it will never register. It violates the standard, immensely comforting formula of the locked room mystery, the formula that makes Christie’s books so compulsively readable: There is meant to be one killer per crime, a single figure whose motive, means, and opportunity all become clear at the end in a single shining moment of revelation. The fact that everyone is suspicious is just camouflage, meant to distract readers from the hidden truth.

By making all of her suspects the collective killer, Christie uses the familiar murder mystery structure as her greatest red herring. The misdirect lies not in any of the clues Poirot is examining, but in the reader’s learned, unconscious knowledge of how murder mysteries work.

And that makes the ultimate reveal all the more astonishing and delightful. Christie isn’t the one deceiving the readers, in the end — the readers deceive themselves.