Courtesy of Fox Searchlight Pictures

One of the many humorous scenes to balance out the cruelty of forlorn hope that paints “Three Billboards Outside Ebbing, Missouri” comes served by Penelope (Samara Weaving), the vacuous 19-year old girlfriend of Mildred Hayes’ (in a phenomenal display of stoicism from Frances McDormand) ex-husband, Charlie (John Hawkes). Charlie, quoting his partner half his age, tells Mildred, “violence only begets greater violence,” a line she admits to having borrowed from “a bookmark … from a book I was reading” about polio or polo (the one with the horses). It’s played out with excellent comedic timing and dramatic suspense, the scene suspended by an uncertainty of whether Mildred will erupt with fury at the thought of her abusive ex-husband sabotaging her plans of finding their daughter’s murderer.

“Three Billboards” is a black comedy grounded on this principle platitude. Its through line is inherently violent, underscored by themes of revenge and Southern Gothic degeneracy (and redemption). In the opening, cinematographer Ben Davis recalls the isolation of Tarkovsky’s scenery, with the titular billboards shrouded in fog. On a road infrequently traveled, Mildred drives home and sees the unused billboards. She stops, reaches an epiphany. With $5,000 cash, she rents the billboards from Red Welby (Caleb Landry Jones in a performance that is a whole lot less slimy than his previous work), the bumbling — but kind — owner of the advertising agency and the three billboards.

They read: “RAPED WHILE DYING,” “AND STILL NO ARRESTS,” “HOW COME, CHIEF WILLOUGHBY?”

The victim of the crimes described by the billboards was Mildred’s daughter, Angela. Less than a year ago, Angela was violently murdered, and the perpetrator has yet to be found. Meanwhile, the Ebbing Police Department hasn’t made an inch of progress on solving the case. For Mildred, the billboards’ public shaming is her only grasp of hope that her daughter’s murderer can be brought to justice. There’s a revenge story somewhere here, but the crux of Martin McDonaugh’s screenplay is much more human than that. What begins as a reopening of a cold case evolves into an exploration of cyclical violence, where grace begets more catharsis than a bloodied act of vengeance.

McDonaugh is reticent to cast judgement on the folks of Ebbing. Just when you predict you’ve got your moral compass figured out, he throws a cog in the wheel of your rationale and leaves you to put the pieces together. Amidst the comedy — because it is certainly a funny film — are uneasy questions that ask us what it means to be “good.” Murder isn’t good, nor is rape, but these are simple reflections that “Three Billboards” circumvents, casting nuances on definitions of morality. A good man is hard to find, something McDonagh (and Southern Gothic illuminary Flannery O’Connor) understands; life is rarely so black and white, after all.

Not since “Fargo” has McDormand delivered such an arresting performance in a leading role. It’s only right, considering that director Martin McDonaugh (“In Bruges,” “Seven Psychopaths”) wrote the character with McDormand specifically in mind. Once the billboards are the talk of the town, Mildred becomes public enemy number one in the small town of Ebbing. Officer Dixon (Sam Rockwell), a cop rumored to have tortured black men (judging by his liberal use of racial slurs, these rumors are likely more than mere rumors) and a mama’s boy comic nerd, almost becomes a pervasive threat to Mildred for her audacity to challenge him. Almost. McDormand fires verbal retorts with a satisfying strain of venom that never fails to excite; she’s a unrelenting firebrand who rarely shows any intent on wavering in her search for answers. For as commanding and assertive as she is, when she unfolds and displays compassion, it comes across as genuinely surprising. She makes an unlikely friend in the person she directs her anger toward the most, Chief Willoughby (the consistently great Woody Harrelson), and their relationship takes wholly unexpected turns that shade the film in emotionally stringent ways. Much of her power comes from the way she expresses herself with just her face; she’s able to express so much by doing so little, a feat that few can claim.

Verdict: “Three Billboards Outside Ebbing, Missouri” is a stimulating meditation on the nature of violence and revenge bolstered by what very well may be the greatest performances of Frances McDormand’s career. What Martin McDonagh’s screenplay achieves is nothing short of perfection.