Martin McDonagh’s Three Billboards Outside Ebbing, Missouri will definitely be one of the most talked about, and most contentious, movies of the year. This sprawling Midwest invective takes on police incompetence, brutality against people of color, and sexual assault, with heavy doses of small-town racism and sexism. It’s wildly entertaining; you truly don’t know where McDonagh is going. But don’t assume the movie has anything profound to say beyond that.

Frances McDormand’s Mildred, a contemporary Medea bent on avenging her daughter’s rape and murder, has waited seven months for answers. Frustrated that the cops have done nothing, she purchases three billboards on a seldom-traveled side road to get their attention. It works. Her billboards are a wake-up call to the sleepy town, stirring up tensions that escalate and explode. She specifically calls out Chief Willoughby (Woody Harrelson), who the whole town knows is dying of cancer. And then there’s Dixon (Sam Rockwell), the unabashedly racist officer, who can’t contain his outrage as diplomatically as Willoughby.

I am always here for a Frances McDormand movie, and Mildred is a role she inhabits as if she wrote it herself. McDormand is good because she’s natural, with few big-acting tricks intended to impress us. Her sourness and lack of pretense seem like they belong to the real McDormand; even when her character breaks down, fraught over her daughter’s abuse and death, McDormand doesn’t overplay the tears. Mildred’s righteous anger brings her to the edge of the line, and then over. At what point does she take it too far, and become her own villain?

The movie doesn’t pass judgment on her path to vengeance. We understand the grief that underscores every move Mildred makes. But McDonagh’s script overall does have a complicated way of casually tossing off his usual non-P.C. comedy. Many of McDonagh’s plays, plus his first movie In Bruges, delight in the offensive wordplay of his fellow Irishmen and women. In McDonagh’s mind, the small towns of Inishmaan and Leenane might translate to America, with their offhand racism and musical vulgarity–and their comically gruesome violence.

But Three Billboards starts from the rape and murder of Mildred’s daughter Angela, a horrific launching point. There are flippant jokes about police brutalizing black people that, sure, are funny; it can feel good to laugh in recognition of an incredibly painful conversation we’re going through nationally. But these asides are window-dressing, solely intended to mock dumb cops and this small town’s backward way of life. Mildred is an ally of black people, we see, because some of her friends (including her shop employee) are black. There’s also Peter Dinklage, who saves Mildred from a jam (because he has a crush on her), and who must endure a series of midget jokes from the whole town. He’s condescended to, like many other people hurting in this community; but he’s mostly there for local color and not for larger observations about bigotry and closed-mindedness.

Among the fully realized characters we do get are Willoughby and Dixon: the good-hearted family man cop trying to do his best; and the white-trash redneck screw-up who earns a second chance. McDonagh is much better writing real people than whipping out shallow punchlines. Harrelson’s Willoughby has some great scenes with Mildred, where he’s clearly searching for ways to empathize and find some commonality. After all, it’s his community that’s been damaged, too. Rockwell is weird and wonderful as a man who still lives with his mother, drinks excessively, and is dumb as a bag of sand. But he’s really an overgrown adolescent, driven by his (undoubtedly stupid) instincts, heedless instead of thoughtful. His story is a redemption arc; in this depressing town, we need someone to believe in. These actors, and McDormand, overcome the more juvenile aspects of McDonagh’s often engrossing, sometimes thoughtless vision.