The Outfit is one of those films that rewards your lowered expectations, which probably doesn’t make it sound too good. What I’m trying to say is that, in its old-fashioned, low-key way, The Outfit, currently playing in theaters, is better than you might expect for a modest film that’s not exactly being hyped to the sky. It has sequences that work well, certain odd interludes of effective tension broken by pleasantly unexpected humor, and an overall tonal quality that’s satisfying if you’re in the right mood. There are problems — the film drags badly in the middle, and there are some implausible plot developments among the many twists and turns, as well as some weaker performances among the strong ones.

But it reminded me of how, in the old days, when people still had leisure time, this would’ve been an enjoyable movie to stumble upon when you had a few hours to kill and went to the theater to see what might catch your interest. Or it would’ve been a pleasure to discover on television late one night, when you’d be flipping channels in a desultory way, looking for something with compelling facets to tide you over in an insomniac interlude. Good times, though we didn’t realize it then.

Mark Rylance is the obvious reason to see the film — he’s an actor you could watch for ten hours straight. He’s so brilliant at building a character detail by detail, making you believe in the existence of the person he’s creating by the way he wears his slightly bent gold-rimmed eyeglasses halfway down his nose, or smokes a calming cigarette, or runs his hand gravely over his thinning, neatly combed-back hair.

But the film also has a premise I like, about how you should never underestimate anyone when you first encounter them, because you don’t really know who you’re dealing with. This is good life advice, as well as a common premise for a variety of film genres I tend to enjoy: action films, Westerns, film noir, Chinese martial arts films. The Outfit is listed as a crime drama, but it leans toward the unassuming indie side, with the entire film set in and around the impeccably maintained tailor shop owned and operated by Rylance’s character, Leonard Burling.

Burling is routinely dismissed as “a tailor” by people who patronize his shop and don’t understand his insistence that he’s actually “a cutter,” someone extensively trained on Savile Row in London who’s able to make complex garments from mere bolts of fabric, taking them all the way through the “228 steps” it takes to create a man’s suit. In fact, he’s got a background even more complex than that, but his insistence on the impressive “cutter” skills are an indication that people dealing with him should try to be as careful and attentive as he is.

They aren’t, of course, or there wouldn’t be any movie.

British transplant Burling makes bespoke suits for mobsters in 1950s Chicago, apparently because they’re the rare men who are still interested in wearing sharply cut suits in an age increasingly inclined toward casual wear and blue jeans. While he sits sewing with steady concentration, gangsters walk in and out of his shop, availing themselves of a drop box at the back of the store, leaving and picking up illegal packages. The Boyle family, Irish mobsters who control the neighborhood, are his best customers.

Trouble is brewing on multiple fronts. Burling has a sweetly paternal relationship with his young shop assistant, Mable (Zoey Deutch), a tough-minded local who has big dreams of escaping her crime-ridden neighborhood. But she’s secretly dating Richie Boyle (Dylan O’Brien), son of the mob boss. Nepotism makes dim-bulb Richie the second-in-command, but he’s all too jealously aware that his father’s enforcer, the far scarier Francis (Johnny Flynn), is considered more qualified to run the show — especially at an uncertain time when the Irish mob is trying to push out the black gang that preceded them in the numbers racket, the LaFontaine crew.

On top of the potential gang war, there’s rumored to be a rat infiltrating the Boyle family, feeding information to the FBI via secretly recorded tapes. As the volatile situation erupts, Burling finds himself and Mable thrust into the center of violence and danger, relying on their wits to survive the night.

Rylance, a noted stage actor and leading light of British theater who came to greater public prominence in the BBC series Wolf Hall and has gone on to meaty roles in films like Bridge of Spies, Dunkirk, Trial of the Chicago 7, and Don’t Look Up, is almost the whole show. But he gets able support from Deutch (Set It Up, Buffaloed) as Mable — she’s the daughter of director Howard Deutch and actor Lea Thompson (Back to the Future). Together they do admirable work on early scenes especially, communicating their affection for each other as well as their regret that she can’t really be the daughter figure Burling would like her to be, the one who learns his trade and inherits his shop. There’s a memorable scene involving the folding of expensive silk pocket handkerchiefs on opposite sides of the same display table — he does it reverently, exquisitely, each handkerchief a perfect square resting lightly on the soft pile, while she does it faster and less precisely, then with increasingly deliberate carelessness, the edges not matching up, until, by the end, she tosses a messy, barely folded triangle on top.

It’s a silent argument, Burling’s steady attempt to educate and persuade Mable “what a square looks like,” as he puts it humorously, and her ever more adamant refusal. And of course, the scene has further implications about their disparate approaches to life and goals, which are going to have consequences later.

It’s a small pleasure if you like that sort of thing. That describes all the better aspects of this actor-oriented film, which represents the directing debut of screenwriter Graham Moore (The Imitation Game). Flynn (Emma, The Dig) is nicely menacing as Francis, and Simon Russell Beale as mob boss Roy Boyle is, as always, a reliable old pro. Nikki Amuka-Bird is striking in a brief role as the flinty head of the LaFontaine crew. Weaker link Dylan O’Brien (Maze Runner, Transformers) is a heartthrob type who does little other than look cute in the Richie role, and a number of actors in smaller parts aren’t so hot either. But all is forgiven if you can somehow get yourself into that old-fashioned mood of mild, tolerant movie-watching, as if you had all the time in the world.