This review may contain spoilers. I can handle the truth.
Nathan Phillips’s review published on Letterboxd :
This review may contain spoilers.
Agatha Christie's dim view of humanity is such that a story about a collaborative murder involving twelve people becomes somehow the height of warmth and optimism, by her standards, because the victim is a child killer. Lumet's glee at such perversity -- underlined in a climactic flashback painstakingly detailing the stabbing -- offsets the hamminess of several members of his once-in-a-lifetime cast, Albert Finney's Hercule Poirot the silliest of all. Others including Lauren Bacall, Sean Connery, Ingrid Bergman (who won her third Oscar for it, bizarrely), John Gielgud and numerous others appear in what are really just walk-ons... but the standouts are easily Rachel Roberts, as the duplicitous maid Hildegarde, and Anthony Perkins as (of course) the most nervous of the suspects, Hector; everybody else is kind of superficial. Nevertheless, if the thought of a murder mystery set aboard a train with a bunch of your favorite stars excites you there's no reason you won't find this engaging, and as a bonus its amoral finale ensures that it doesn't result in your brain falling out.