In a film about a mother's search for the person or people responsible for the death of her daughter, it's not actually the mystery of that crime that drives the story.
For "Three Billboards Outside Ebbing, Missouri," it's all about the people of the town affected by this one event (and the upheaval caused by three billboards), and how hate or kindness can shape their actions and choices.
For a movie that pits one woman against the police, there are no clear-cut villains (with the exception of one man whose presence in the small town brings up too many unanswered questions). It's easy to side with Frances McDormand's Mildred in her effort to spur police into action after seven months of inaction into the investigation.
However, the police led by Woody Harrelson's Chief Willoughby are neither inept (for the most part) or unfeeling toward the case. It's not a matter of not wanting to solve it, but rather they don't have the evidence to give them a break in identifying a suspect.
That impasse helps the drama unfold as McDormand battles against the police and others in the town who feel she shouldn't attack the department, especially one led by a man with a cancer diagnosis.
It also sets the stage for two powerhouse performances.
McDormand has proven she can carry any film, and she seems to shoulder this one with ease, portraying a grieving mother and a whip-smart woman. McDormand easily throws out the insults and obscenities that have marked the dark comedies of director Martin McDonagh ("In Bruges").
Rockwell plays an entirely different character - one slow on the uptake who can't battle McDormand or Harrelson in conversation - but one who manages to have the most drastically changing arc in the film. He manages to play the bumbling idiot, the violent racist and the penitent outcast all in one movie.
Though the two actors are clearly the best part of the film, they get plenty of support from the majority of the cast. The only exception is Abbie Cornish, whose age and native Australian accent make her stand out in a movie supposedly centered around a small town. Cornish is usually a superb actress (who can easily fake an American accent), but she's too young to play the wife to Harrelson's character, especially in a movie that makes fun of one man (John Hawkes) for dating a 19-year-old (Samara Weaving).
The film isn't without other faults - it's a little dismissive of the racial overtones without giving much substance to its black actors, and an antagonist seemingly appears out of nowhere for no reason - but it's a solid movie driven by some of the best performances you'll see in a movie all year.