Kenneth Branagh, who also directed, portrays Agatha Christie’s legendary detective Hercule Poirot in “Murder on the Orient Express.” (Photo Credit: Nicola Dove/Twentieth Century Fox) )
Book world editor

There’s a nagging mystery at the heart of “Murder on the Orient Express,” and it has nothing to do with homicide. It’s all about a mustache — specifically, the one on the face of renowned Belgian detective Hercule Poirot, played by Kenneth Branagh.

A viewer must know: How was this hirsute sculptural masterpiece created? The gray accoutrement has layers upon layers of bushy swoops, and it's so mystifyingly intricate, it often distracts from whatever else is happening.

Most people may already be acquainted with the plot (not to mention the culprit) of Agatha Christie's novel, which was already famously adapted by Sidney Lumet in 1974. That means Branagh, who also directed the film, has a tall order, making a familiar tale worth revisiting. With a script by Michael Green, the story takes place in 1934 and follows Poirot as he investigates the murder of a man on a train marooned by an avalanche.

The fourth adaptation of Agatha Christie's 1934 novel stars Kenneth Branagh, Penélope Cruz, Willem Dafoe, Judi Dench, Johnny Depp, Josh Gad, Leslie Odom Jr., Michelle Pfeiffer and others.

The victim, Edward Ratchett (Johnny Depp, playing it relatively straight for once), was a shady art dealer with plenty of enemies, so not even his associates seem surprised when he winds up stabbed to death. But the guilty party is almost certainly still on the train, which leaves about a dozen possible suspects.

The trick with such a sprawling cast is for the characters to efficiently make individual impressions. That works with some — especially Josh Gad’s sneaky Hector MacQueen and a flirtatious widow played by Michelle Pfeiffer. Mostly, though, the big-name cast is wasted, leaving Willem Dafoe, Judi Dench, Olivia Colman and Penélope Cruz with little to do. They fade into the background behind Poirot, an eccentric man who doesn’t shy away from reminding his fellow passengers that he’s the greatest detective alive.

Josh Gad, left, and Johnny Depp play murder suspects. (Photo Credit: Nicola Dove/Twentieth Century Fox) )

Those bombastic pronouncements are quite funny, and early on, “Murder” excels at delivering laughs. For a moment, the movie seems to be going for a daffy vibe, in the vein of “Clue.” But the story eventually settles into a somewhat lethargic procedural as Poirot takes turns interviewing so many one-dimensional characters, eventually uncovering one shocking twist after another.

“Murder” may lack urgency, but it does have style. The sets, the costumes and the vistas are stunning. And cinematographer Haris Zambarloukos — a frequent Branagh collaborator — gets inventive filming inside cramped quarters, occasionally capturing the action from overhead or documenting a scene from outside while panning past the train’s windows.

But like Poirot’s mustache, these little flourishes don’t necessarily pull viewers deeper into the story so much as make them step back for a moment of artistic appreciation. There’s nothing wrong with, on occasion, prizing form over function. But things have gone too far when a murder mystery in a whodunit plays second fiddle to a personal-grooming puzzle.

PG-13. At area theaters. Contains violence. 114 minutes.