Murder on the Orient Express is a buffet, occasionally tasty, supplied by actors offering unlimited servings of ham.
The classic Agatha Christie story is an ideal vehicle for dream cast showboating — a 1903 murder on a Paris-bound train stuck in to Yugoslavia, offering 12 suspects, 12 lavish costumes, 12 outrageous accents, and 12 garish character traits, brandished by actors who perform as if they've been well-compensated and handsomely housed. Happy to be there, happy to be entertaining us.
Kenneth Branagh — he also directs — is genius Belgian detective and person-attached-to-a-mustache Hercule Poirot, Judi Dench as an imperious aristocrat named Countess Dragonbreath (or something), Josh Gad is a tubby sidekick, and Johnny Depp plays a self-obsessed weirdo (not much of a stretch).
Nobody seems to care that Branagh has given the plum role to himself, or lavished so much attention on Poirot, Christie's version of Sherlock Holmes, a likable know-it-all who somehow makes arrogance look good. Poirot has slightly better manners, and (as played by Branagh) a form of OCD — he likes his boiled eggs (and other things) to match precisely.
Asymmetry gets under his skin, and this eye for slightly-out-of-place detail makes him a good detective, as we see during Poirot's scene-stealing entrance at Jerusalem's Wailing Wall, where he solves a crime and deploys his walking stick in a way that proves he is several chess moves ahead of the culprit, and the crowed.
The titular crime is a harder nut to crack. It occurs under Poirot's very nose, yet the deed proves very difficult to solve — due not to a deficit of suspects, but a surplus. Everybody seems to have a motive, and everybody — including governess Daisy Ridley, creepy German Willem Dafoe, husband-hunting divorcee Michelle Pfeiffer — seems to have an alibi. Poirot's high opinion of himself is tested — he's accustomed to knowing more than everybody else, and here the situation is reversed.
The plot sticks to Christie's original — Poirot eventually deduces that a great many of the passengers have some connection to a sensational murder that occurred some months earlier in the U.S. (Christie modeled this crime-within-a-crime on the Lindbergh kidnapping). Yet the more he learns, the more clouded a solution becomes.
Branagh the actor finds a nice balance between Poirot's colorful flourishes and his moral seriousness. Branagh the director gives the movie the same balance, and wants the audience to have as much fun as the actors, which is true more often than not.
He also leaves Christie's famous ending more or less intact. That makes sense — at this point, why take another stab at it?