Frances McDormand plays a woman trying to shame a police chief.

One way you know a film is written by a playwright is when everything everyone says in it is clever and wise and perfect. Three Billboards Outside Ebbing, Missouri, written and directed by Martin McDonagh, never fails on this score. The dialogue, particularly when given life by actors Frances McDormand and Sam Rockwell, is hilarious and provocative. Rockwell in particular, as a dim-witted, violent, racist mama's boy redneck cop, was born to speak these lines.

Another sign that a theater person is in charge is that the story is all about the uncanny way that seeking revenge always makes everything worse, a reliable engine of drama since the form was invented.

But the biggest indicator that you're watching the work of a playwright is the sense that there's no way the story is what the film is really about. The three billboards in Three Billboards are signifiers and catalysts, but they're also red herrings (literally red, in fact).

The billboards are taken out by Mildred (McDormand) as a way to publicly shame Ebbing's police chief (Woody Harrelson) for having failed to catch the man who raped and murdered her daughter. They also keep her grief alive and present tense.

"RAPED WHILE DYING," reads the first one, followed by "AND STILL NO ARRESTS?" and then "HOW COME, CHIEF WILLOUGHBY?"

The signs cause a huge stir, leading to heavy consequences for everyone. And though you revel in Mildred's vengeful zeal (McDormand is as good as an actor can be in this complex role), her single-mindedness begins to run aground of the suffering she is causing others. Her capacity for tenderness hasn't been erased—it comes out in three tiny, heart-bursting moments—but she suppresses it in the quest for justice.

Her true fear is that "there ain't no god and the whole world's empty and it don't matter what we do to each other." But she's not above kicking little kids in the crotch, either.

McDonagh depicts graphic violence and hateful language flippantly, in a style people like to call Tarantinoesque. One particularly gruesome beating, elaborately staged in a long single take, feels like a nod to the maker of Pulp Fiction, as well as an effort to ensure this film feels "cinematic."

But McDonagh is not a shock artist, not satisfied milking the disjunction of liking the bad cop or the mean lady. He's making the case that humans are complex, that "sympathetic" is relative, and that whatever horrible things people are capable of doing to each other (and they are indeed horrible), we still have to live together when we're done.

This strikes me as an especially Irish kind of cosmology—one that arose naturally in a country divided by religion and empire for hundreds of years. But it also applies to the American South, and outward to all of America, which is similarly divided by those same forces.

The Irish Southern Gothic cocktail feels timely to 2017 America on many levels, not least in its deeper message about the troubling relationship between justice and compromise.