Any movie that insists on a dwarf joke every 10 minutes is either desperate or stars Leslie Nielsen — or both. Leave it to the acclaimed Irish playwright Martin McDonagh (“The Pillowman”) to find a new excuse for such deployment in “In Bruges,” his first full-length film as a writer-director. This playful — if exceedingly gory and morally scrambled — riff on British gangster tropes wants to be a profane fairy tale of redemption. And as the story is set in the titular Flemish city, touristically abundant in its cobbled, 12th-century charm, why shouldn’t there be a dwarf to complete the picture and lead the fallen protagonist on his way?

Two characters could scarcely be more out of place than Ray (Colin Farrell) and Ken (Brendan Gleeson), a typically mismatched pair of London hit men who have been sent on a sudden trip to Bruges by their boss, Harry (Ralph Fiennes), after a job has gone horribly wrong. They’re supposed to check into a hotel and stay there until the trouble blows over and, presumably, they’ll receive further instructions.

While the avuncular Ken takes to the town’s historic attributes, waxing poetic and ascending the twisting stairs of the medieval bell tower, the restless Ray is bored out of his skull. Against his better judgment, the elder mobster lets the kid slip out of his grasp, and before long, Ray has fallen in lust with a lissome Dutch beauty named Chloë (Clémence Poésy) whom he spies on a film set he strangely comes across. (And, hence, the dwarf — played by Jordan Prentice, in the cranky, unsentimental manner of Peter Dinklage.)

Suddenly, Ray warms to his cursed exile, meeting Chloë for a first-date dinner that erupts into violence when he attacks a Canadian couple who complain about cigarette smoke. Throughout the film, which got a lukewarm reaction when it opened the Sundance Film Festival last month, such instances are shot as if meant to be deeply satisfying, engendering a coziness with loutish temperament. Apparently, for Ray, it’s the magic touch.

Chloë, rather than fleeing in horror, is impressed, and she lures the hit man back to her place for a nightcap. Their liaison is interrupted when a local thug breaks in and sticks a gun in Ray’s face. Turns out he’s not her angry boyfriend, but an accomplice in a scam to fleece tourists. This being a McDonagh screenplay, however, it’s a matter of mixed signals. Ray handily snatches away the gun, which is loaded with blanks, and proceeds to blast the feckless skinhead in the eye, offering homophobic invective that doubles as professional advice.

Clearly, there is no such thing as a quiet layover for Ray. But as flashbacks unfold, the audience learns why he’s been dispatched to the purgatorial sidelines, and it’s terribly evident why Mr. Farrell’s famous eyebrows are so fervently knitted all the time. Within the honor-bound society to which he has enlisted, Ray has committed an unforgivable sin, and when the phone finally rings and Ken picks up, it’s no surprise what hardball Harry tells him to do next.

The movie’s weird modulations tend to serve Mr. McDonagh’s love of wild-hair dialogue rather than a consistent dramatic narrative. So as Ken (given an autumnal air of mordant wistfulness by Mr. Gleeson) ponders his orders, he winds up on an all-night bender with Ray. The dwarf, whom Ray constantly confuses with a midget, comes back into play, as do two prostitutes, a pocketful of drugs that Ray has swiped from Chloë, and the dwarf’s bizarre rambling monologue about a global race war. It’s nutty stuff, wholly inspired, and yet it doesn’t seem to belong in the same movie — other than to compel sympathy for Ray, whom Mr. McDonagh wants us to see as Ken does. Okay, sure, he’s a charming, screwed-up guy who may not always be a danger to society, but he really does deserve his fate.

When Harry comes to Bruges to enforce the code, the movie spins further into its own peculiar ether. It’s as if the drugs ingested by Ken and Ray have seeped into the celluloid. Here is Mr. Fiennes relishing his “Sexy Beast” moment as a truly foul piece of work whose East End toughness is leavened by an absurdly funny delivery of dialogue that can’t be printed in this newspaper. That the more-or-less doomed Ken and Ray are — Canadian tourists aside — two of the nicest hit men you could ever hope to shoot you is one of the movie’s many hedges, but easy to concede because the actors are so good — even Mr. Farrell, who has squandered too much of his equity in recent years on crappy paydays like “Alexander.” If the movie can’t resolve without one last dwarf joke, it is perversely logical, and exactly the problem.