There are spoilers ahead. I strongly recommend you to watch the movie before reading this.
It's not always you find yourself watching a movie where the plot is present only to play the role of a pivot around which an immaculate cast can wow you for a hundred minutes. Don't get me wrong, Three Billboards has a compelling plot. However, what's put in front of you as the plot does not advance insomuch as everything around it. The world around the plot changes while it remains the only constant, reminding us why we are in Ebbing, Missouri in the first place.
Missouri, like most other midwestern states, is studded with small sleepy towns which to the world outside may as well not exist. Ebbing is one such sleepy town. The movie begins with Mildred Hayes—played by a fantastic Frances McDormand—buys three billboards outside the town to ask hard questions about a case that remains unsolved after seven months. The case in question is the rape and murder of Angela Hayes, Mildred's young daughter. How the billboards shape the future of the town and the people involved over the next few months is what the movie is about.
Woody Harrelson plays an outstanding Chief Willoughby, a sliver of good, in a town full of cops drunk with power—at least as much a small town cop can be drunk with. The police couldn't find any clues connected to the murder and Mildred wants to know why they aren't working hard to catch the murderer. The billboards become the talk of the town, and they actually get the police to revisit the case because of the all the attention it's getting. However, the Chief dies in the end, the murder remains unsolved and there is a consolation where Dixon—played incredibly by Sam Rockwell—ride to Idaho to feel better about taking some action, though it wouldn't help their cause.
Though the entire movie is a dialogue writer's dream, I enjoyed the evolution of Dixon, from a clueless young cop to a changed man, having been introduced to love and forgiveness. Caleb Landry Jones plays a young man named Red Wilby who at one point gets thrown off a window by Dixon. There is a scene in a hospital room where Dixon is admitted with burn injuries after getting caught in a fire accident. It happens to be the same room where Red is also recovering. With Dixon's face completely covered by bandages, Red approaches him, asks how he is doing, and offers him some orange juice. Dixon, a changed man at that point, starts crying on seeing what he's done to the kid and the kindness the kid's showing. He apologizes and the kid then realizes that it is, in fact, the guy who threw him off a window. This is the moment that won me over and showed for a fact that Dixon will never again be the same. I'd expect the kid to revolt knowing that this is the guy because of whom he's in a hospital badly injured. But Red, even at that moment, asks Dixon to stop crying because the tears would make his burns worse. Dixon responds with "Isn't salt good for your wounds though?" The kid with care and forgiveness in his voice responds with "What do I know? I'm no doctor." and you don't see him for the rest of the movie. For me, this scene was the surest sign that Dixon is going to do good and nothing else in the days to come.
Willoughby, before shooting himself at one point in the movie, leaves letters he's written to the people he cares about. The whole montage of the letter being narrated in Woody Harrelson's voice will haunt you for days. The fact that Martin McDonagh wrote a bunch of small story arcs about people and places, is what probably qualified Three Billboards for all the awards its won—and will win in the future, deservedly so.
In Red, the story tells us that a little compassion goes a long way. In Dixon, it tells us that you don't stop learning lessons, ever. In Mildred, it tells us that closure is something you should find in a form or manner that suits you and works for you. That it just doesn't happen.
All in all Three Billboards Outside Ebbing Missouri is the kind of movie that perhaps what defines a movie to me—something that introduces you to people, places, and tells their stories and lets you to make of it what you will.