Mildred Hayes seethes with rage when she storms in to an advertising agency in her backwater hometown and demands to know how much it will cost to put a message up on three dilapidated billboards situated on an under-utilized stretch of road near her house. Her rage is perfectly understandable. Months have gone by since the brutal rape and murder of her teenage daughter, and, in the hands of the local police department, the case seems to be going nowhere.

There's an unceasing, violent intensity to Mildred, played by the great Frances McDormand, to which no one - not even the person she's trying to purchase advertising from - seems immune. It does not boil over in this case, but the threat looms ever-present - there on the surface even if it's not always expressed to its fullest extension. 

As McDormand steams, the camera is trained for just a moment on a windowsill in the office where an insect writhes in futility, stuck on its back and unable to flip over. You fully expect McDormand, positioned by the window, to crush the struggling bug. It'd fit with her demeanor. Instead, she gently flips it over.

So is the tone set for Three Billboards Outside Ebbing, Missouri, a film that cuts the raw anger of its principal characters with small, unexpected kindnesses, and in so doing becomes a gem. Writer and director Martin McDonagh couldn't have known how well this would sum up America's 2017, and what it might need to move beyond it, as he was crafting this story. Indeed, it seems unlikely he set out to do anything of the sort. 

But perhaps it takes an outsider (McDonagh is Irish) to diagnose what collectively ails us and prescribe a suitable remedy. Three Billboards - whether intentionally or by happenstance - seems to capture perfectly the almost unending awfulness of recent months, to understand what's up in our imperfect Union. 

Almost everyone in Ebbing seems to carry around their own darkness. Chief Willoughby (Woody Harrelson) - the head of the police department called out by name on Mildred's billboards - grapples, mostly privately, with his grief and his own mortality. One of Willoughby's deputies, Dixon, a dimwit ridiculed by seemingly everyone in town (often justifiably), struggles with his own rage, expressed most often with vicious violence. Dixon is played brilliantly by Sam Rockwell, and though there is no obvious source of his anger, as there is with Mildred's, you come to understand it nearly as well. He is mocked ceaselessly - for being unqualified for his job, for living with his gruff mother, for being an unintelligent goon. These are all fair criticisms of Dixon, but they come with cruelty and without any compassion for the man. As McDonagh slowly reveals, Dixon - flaws and all - has much good to him as well.

Many of the supporting characters, from Mildred's son Robbie (Lucas Hedges) and ex-husband Charlie (John Hawkes) to Willoughby's wife Anne (Abby Cornish) to a townie, James (Peter Dinklage), caught up innocently in all of this, seem defined by their anger as well. And yet it is the kindnesses - from one character to another to another - that define this film. It is those moments, as much as it is McDonagh's now-trademark blackest-of-black comedy that keeps Three Billboards from being suffocating, and, in turn, almost makes it uplifting.

It is Willoughby's parting charity to Mildred. It is one of the men Dixon has beaten offering him orange juice when he ends up in the hospital bed beside him. It is a bottle of wine given to two people who don't deserve it. It is a husband sparing his wife, a moment of peace with a wild animal that has snuck closer to humans than it should, and a deposed officer of the law delivering a day of hope that justice will finally be done.

Three Billboards Outside Ebbing, Missouri has much of what we've come to expect from McDonagh - a caustic wit and sudden, stunning instances of violence. But it is at its best - it is a real treasure - when it plays against type and delivers modest but indelible moments of humanity against a backdrop of unspeakable tragedy.