“In Bruges,” like its title, is completely unassuming. The film is the first feature-length by Martin McDonagh, an Irish playwright, who, at his better moments, can be placed in a tradition of Irish drama that dates back to Samuel Beckett. Indeed its choppy and suspenseful dialogue is reminiscent of the work of Harold Pinter and David Mamet.

The film is black comedy in that it treats subjects traditionally taken seriously — like murder — in a humorous manner. However, the dark humor is ultimately limited to its dialogue and never fully realizes the fatalism and satire characteristic of the genre.

Ray (Colin Farrell) and Ken (Brendan Gleeson) are two hired hit men who — after a botched attempt at murder back home in London — have been sent to an obscure tourist town in Belgium to await instructions from their boss, Harry (Ralph Fiennes). It’s funny because Ray and Ken are killers who have to find ways of entertaining themselves in Bruges, a nondescript medieval town. Ken delights in Bruges’ history and art while Ray, like a spoiled child, is bored to death. To complicate matters further, Ray has recently murdered not only a target but an innocent child by mistake.

This premise has the potential for effective black comedy, and Ray and Ken’s conversations about sightseeing, though absurd, betray their unspoken sadness and terror. But ultimately McDonagh gets caught up in not so funny, politically incorrect humor. Ken, trying to persuade Ray to go look at churches with him, says that “we shall strike a balance between culture and fun.” Ken replies, “Somehow, I believe, Ken, the balance will tip in the favor of culture, like a fucking black retarded girl on a seesaw … with a dwarf.” This is, obviously, the most extreme example.

At some of its best moments the film’s threads come together to create a fatalistic vision characteristic of self-conscious, postmodern plot construction. At the end of the film, Ken, who is on the brink of death, decides that before he dies, he still has a chance to save Ray’s life because Ray is a good person and deserves to live. Ken, who’s bleeding at the top of a tower in Bruges, leans his dying body over the edge of the tower to get a shot at the bad guy, but after a long, laborious, painful struggle, all he can see from his precipice is fog. At this moment our awareness of the writer’s control over the lives of his characters is effective because it resonates with the ways that cruel fate can govern our own.

However, the artificiality of “In Bruges” does not always have such power. During the last third of the film, the author’s presence is not so much ironized as just annoying. In a meta moment, Harry tells an innocent bystander to shut up because “this is the shoot up.” Instead of laughing, we conjure an image of McDonagh sitting in a cloud somewhere above Bruges smugly pointing out how smart he thinks he is. And at the end of the film, the disaster that befalls all the characters seems neither tragic nor tragicomic, just fake. Everyone’s dying, but it’s not that upsetting.

The film is missing an ingredient of postmodern fiction that can make other works so described very human despite the way they emphasize their own artifice. Like other postmodern works, there is no attempt on the part of the author to place his characters in a reality that exists before and after the film. But the unreality of “In Bruges” does not end up lending itself to real drama. The black comedy lies only in the characters’ dialogue and not in their fates.

Toward the end of “In Bruges,” the characters all of a sudden start caring about each other, and we are meant to feel wholeheartedly sympathetic. But this kind of human drama seems incongruous after all the inappropriate humor about midgets and black people.