Now deep into the second half of his career, Liam Neeson has found an unexpected niche in a series of action-hero roles that leverage his weatherbeaten looks, his towering height and the gravitas that’s been his calling card since before he was old enough to have properly earned it. He’s matured into this persona, in a weird but oddly satisfying reversal of the usual path taken by actors who start off with bubble-gum projects only to graduate to more nuanced work. The fact that many of these new films of his aren’t very good is almost besides the point: Neeson can do whatever he wants at this point, and if what he wants is to be a tough guy, more power to him.

But in Scott Frank’s A Walk Among the Tombstones (rated R), we finally get a Neeson action stew that doesn’t skimp on the serious-actor seasoning that flavored his work for decades. The 62-year-old actor is convincing playing men whose actions are informed by life lessons, but in films like Taken, The Grey and Non-Stop those experiences were treated like affectations; in Tombstones, Neeson makes us believe his character’s ghosts are walking right beside him. That difference – and a complex plot, well told – make this seemingly throwaway genre film one of the surprises of the season.

Based on one of a successful series of crime novels by Lawrence Block, Tombstones is pulp fiction through-and-through. Neeson plays Matt Scudder, a former NYPD detective who indulged one too many times in the practice of drinking first and shooting at suspects later. Eight years after quitting the force (the film takes place in 1999, with Y2K alerts everywhere), the reluctantly sober Scudder works as an unlicensed private detective – so he can’t technically be paid for his services, but he also doesn’t have to fear losing said license when he breaks the rules.

A fellow AA member connects Scudder to Kenny Kristo (the English actor Dan Stevens, miles away from Downton Abbey), a well-heeled drug dealer whose wife was kidnapped, held for ransom and murdered all in under a day. Can Scudder track down the trio of anonymous killers? What do you think?

Scudder’s methodical investigation slowly peels back layers of a series of ghastly deeds that don’t end with Kenny’s wife. He finds the first collaborator easily enough, a shambling and weirdly sympathetic sociopath (Ólafur Darri Ólafsson) whose chilling description of the other two men sets the stage for a terrifying second act.

Here’s the thing about action movies: By “action” we usually mean “violence,” and for violence to be meted out there usually must be a sense of moral justification – the bad guys have to be shown doing bad things, or we won’t cheer when they’re dispatched by the good guys. But Taken and other comparable films tend to keep their thumbs on the scale when seeking a balance between their depictions of good and evil. They show us just enough bad stuff to maintain our emotional investment in the hero’s eventual retribution.

Block’s novel doesn’t do that, and neither does Frank’s adaptation. The pair of villains at the heart of this crime story, played by Adam Thompson and David Harbour, are wretched, frightening, intelligent sadists whose motives for their actions are never explained. They kidnap women specifically to torture and murder them, and to torture their husbands by dangling the promise of their return should a ransom be paid. Like Kenny, the husbands are all drug dealers, which adds a dimension of outlaw justice to Scudder’s search for the killers. It also raises the stakes: Assuming you can stand the scenes of extraordinary tension between these smiling psychopaths and their prey, you’ll be as invested as Scudder in watching him find them.

Writer-director Frank has spent time with the underworld before, in his brilliantly adapted screenplays of Elmore Leonard’s Get Shorty and Out of Sight. Those crime stories were leavened by humor, but the only lightness here is a subplot between Scudder and a would-be apprentice, a street kid named TJ (Brian “Astro” Bailey) who can’t decide between being a cartoonist or a PI. It’s a credit to Frank’s grasp of his source material that he resists the urge to make TJ too cute – but then, nothing in A Walk Among the Tombstones could ever be mistakenly for cute. It’s a bleak, often brutal film that’s hard to forget. And I mean that in the best possible way.

(IMAGE: Liam Neeson in A Walk Among the Tombstones. Photo courtesy of Universal Pictures.)