My first exposure to Sidney Lumet came by way of a VHS copy of “Murder on the Orient Express” that I received as a Christmas present, owing to my childhood enthusiasm for Agatha Christie. At the time, I was too nascent a movie lover to know Ingrid from Ingmar, and I devoured the film with more concern for the fidelity of Paul Dehn’s screenplay than for the particulars of the director’s style, from which this star-studded bauble of a thriller is generally considered something of a departure.

But as Lumet, who died Saturday at 86, wrote in his 1996 memoir “Making Movies”: “Good style, to me, is unseen style.” And while it may seem far removed from the gritty Gotham enclaves and the less genteel crime-story tradition in which he thrived, “Orient Express” is a Lumet picture through and through, though it took me more than one viewing to appreciate his deeper, stealthier imprint on the material. Unpretentious, ultra-disciplined, never one to impose an overt authorial signature, Lumet is nonetheless there in the sinister mood that pervades this seemingly frivolous entertainment, and in the subtle moral gravity with which the film weighs its crisis of conscience: When society fails to do its job, is murder justifiable?

In that respect, the Christie blueprint — Hercule Poirot vs. a roomful of suspects — served as an ideal vessel for the story Lumet has been telling for the better part of his 60-plus-year career, in which one man’s principles are pitted against, and tested by, a corrupt and intimidating majority. One can readily detect the theme in “Network” and “Dog Day Afternoon,” still among the high points of 1970s American filmmaking; both are electric, empathetic portraits of men driven to the point of madness and society’s ruthless efforts to contain them. It’s there, too, in the fact-inspired whistleblower narratives of “Serpico” and “Prince of the City,” both studies of police officers battling the NYPD from within, and “The Verdict,” in which an attorney takes the entire legal establishment to task.

Lumet’s social engagement and restless, probing moralism were evident right from the start with his crackling 1957 debut feature “12 Angry Men.” “Murder on the Orient Express” could well have been titled “12 Angry Passengers,” and I can’t help but wonder whether Lumet ever felt a kinship with Christie, who was as prolific and, in some ways, as underappreciated as he was. Like Christie, Lumet has been celebrated more as a storyteller than as an artist, capable of turning out deft, precise crime yarns at a steady pace. Yet he has never quite commanded the reverence or recognition of such Gotham moviemaking icons as Martin Scorsese and Woody Allen.

Lumet, of course, didn’t wield his camera with Scorsese’s operatic verve, and with a few exceptions (“Prince of the City,” “Q&A,” “Night Falls on Manhattan” and “Find Me Guilty”), he rarely wrote his own material as Allen did. He took to features with a no-nonsense efficiency and an unstoppable work ethic born of his many years working in television, happily and at times erratically tackling novels, plays and, in the case of his 1978 flop “The Wiz,” even the odd (very odd) musical.

The fact that Lumet never won an Academy Award for directing places him in distinguished company, though he received five nominations (four for directing, one for writing) and was given an honorary Oscar in 2005. There is some consolation in the number of thesps whom he directed to Oscar-winning performances — the “Network” trifecta of Peter Finch, Faye Dunaway and Beatrice Straight, and, yes, Ingrid Bergman in “Murder on the Orient Express” — which, alongside the memorable turns of Paul Newman in “The Verdict,” Al Pacino in “Dog Day Afternoon” and “Serpico,” Katharine Hepburn in “Long Day’s Journey Into Night,” and countless others, bear out his well-earned reputation as a sterling director of actors.

Lumet’s nimble touch with performers, his ability to draw out great warmth and zesty humor with one hand and coax them toward ever darker, more anguished extremes of emotion with the other, was on gratifying display in his ironically titled final film, “Before the Devil Knows You’re Dead.” The film featured searing performances by Philip Seymour Hoffman, Marisa Tomei, Ethan Hawke and Albert Finney; a time-shuffling, Tarantino-esque structure; and a bracing sexual candor. It attested to the creative vitality and rude good health of a filmmaker whose career most had dismissed as, to borrow the title of his 1988 drama, running on empty.

Amid the stiff competition of 2007, the strongest year for American cinema in the past decade, “Before the Devil Knows You’re Dead” was largely overlooked for year-end awards, serving more as an occasion for critics’ groups to follow the Academy’s example and fete the director’s career at large. Still, to the extent that kudos matter, we should be grateful that Lumet received at least some of his proper due from the industry — one that he had never seen fit to entirely embrace but that needed him no less than we needed the angry men, princes of the city and other brave, crooked heroes he left us.