Frances McDormand is the angry mother of a murder victim in one of the holiday season’s most eagerly awaited films

Three Billboards Outside Ebbing, Missouri, the new release from British writer-director Martin McDonagh (In Bruges, Seven Psychopaths), perfectly captures the mood of our current cultural reality. It does so by dropping us into a highly charged situation right as the flames start to heat things up.

Mildred (Frances McDormand), a steely mother grieving the loss of her daughter (an unsolved murder), has completely lost patience and faith in the local authorities. But she’s far from surrendering to hopelessness. She seizes upon a plan to force Sheriff Willoughby (Woody Harrelson) and his ragtag team of deputies, led by the dim-witted but obstinate Dixon (Sam Rockwell), into action.

Mildred purchases three billboards on the road into town and displays a scathing and quite personal message, a raw plea for justice for her girl.

It matters little to her that the town is so small that everyone will have an immediate and conflicted response to her bold verbal assault. She and everyone in the community knows that Willoughby has done the best he could with the resources available to him. Willoughby is also dealing with his own personal crisis, which renders him decidedly sympathetic, even next to Mildred’s unimaginable loss.

The cultural and political landscape of our world dwarfs the small-town insularity of Ebbing, but social media and the ravenous 24-hour news-cycle create the same kind of fevered immediacy nationally whenever a crime or outrage occurs. So we can relate to what we’re seeing.

Mildred, if asked, would definitely forego talk of mere justice; she’s hell-bent on revenge of the Old Testament sort and it is plain that she would have no qualms at all if she had to dispense it herself. She’s myopic to the point that she fails to see how her quest might have an impact on Robbie (Lucas Hedges), her surviving teenage son, who has to go to school every day in a town reminded constantly of his family’s loss.

During the screening of this film that I caught at the Toronto International Film Festival, I found myself wondering what justice looks like. At the time, in mid-September, I was still focused on police shootings of unarmed black men and white nationalist rallies. Festival entries like this were directly questioning the evolving state of justice without offering easy answers. There was also Black Cop, from writer-director Cory Bowles, about an unsettled black police officer who begins to take out his frustrations on the privileged community he’s sworn to protect, and Dee Rees’ Mudbound, about two families — one black, one white — locked in the eternal quagmire of race in America.

In the end, I could only return to the idea that there is nothing black and white about this complex issue. That is what gives Three Billboards such a necessary role in this ongoing discussion. McDonagh, as is his style, sprinkles in darkly comic flourishes that feel like he’s jabbing our sensitive spots. This makes for recognizable but quite painful truths.

And McDormand is just the right performer to bring this world of hurt to life. She is immersed in Mildred’s own bottomless grief, yet she is also able to imply a glimmer of humor in the infinite sadness that has descended upon her character.

This film faces up to the harsh reality of Mildred’s predicament. McDonagh digs deeper and deeper with the assistance of a talented and fearless cast, who work like canaries in a coalmine to explore the tough ideas of his original screenplay.

Rockwell is another key standout in the cast. As the deputy stuck in a dangerous state of arrested development that allows him to wield his badge and power indiscriminately, Rockwell never allows his character to become simply an object for us to hate or pity, which would have been so easy.

His Dixon hits rock bottom right before our eyes and honestly acknowledges his many faults. The next step, the truly hard work, belongs not to this character, but to us. We must decide how we feel about him and his transformation. It is a performance that U-turns from the typically oddball to a place of humanist redemption.

The film presents justice as a moving target and dares us to actively pursue it en route to a greater good.

(Opens Wednesday at area theaters.) (R) Grade: A