A CAUSTIC vein of dark humour atop lashings of pent-up, anger-filled grief runs through this unmissable tragicomedy. Those familiar with British-Irish writer-director Martin McDonagh’s previous work, In Bruges and Seven Psychopaths, will know what flavour to expect, but this is his most grown-up film to date.

We start with the eponymous trio of dishevelled billboards spaced out at the side of a road that no-one drives down anymore.

Its significance lies in what happened there seven months prior, when teenager Angela Hayes (Kathryn Newton) was raped, murdered and burned. Due to a lack of DNA supposedly leaving the trail cold, the police are no closer to catching the person who did it.

So fed up with the lack of action, Angela’s mother Mildred (Frances McDormand) takes things into her own hands and rents the billboards upon which she puts controversial, attention-grabbing messages. Her 20-foot high, black-on-blood-red words read: “Raped while dying”, “Still no arrests” and “How come, Chief Willoughby?”

This sends a commanding message to the people that should have done something about the crime, particularly Chief Willoughby (Woody Harrelson) himself, as well as openly racist Officer Dixon (Sam Rockwell) who feels especially upset at his boss – and by association himself – being blamed so publicly.

McDonagh brings that same sense of no-holds-barred, foul-mouthed wit and sporadic ultra-violence he’s become renowned for to a story that feels at once universal and bracingly intimate. Its emotional impact feels pulsing and primal, its darkly comedic side standing proud in its own right – in McDonagh’s tale light and dark co-exist, melding together to become one and the same.

It keeps you whipped up with piercing dialogue lobbed like eloquent grenades and truth-filled speeches that will make you want to applaud – like Shakespeare with a potty mouth. But there’s a moral edge to it that gives you lots to chew over, exploring the concept of communal guilt, the inability to take back what’s already been done and the idea of people being willing to share sympathy but rarely wanting to accept their share of accountability.

McDormand leads an array of exceptional performances, playing what feels like an instantly iconic motherly role with a mix of pained sadness and warrior-like determination to get done what nobody else around her seems capable of. You really feel the rage-filled resolve that fuels her every waking moment; anger at the police who haven’t resolved the case, anger at herself for the nasty last words she spoke to her late daughter, anger at the world for simply carrying on.

Harrelson does some of his best work in years (and that’s saying something) as the sympathetic yet tough family man stifled by the demands of his job, trying his best to keep the peace as pancreatic cancer eats away at his insides. He’s a key supporting player whose own story comes into focus in surprising and intriguing ways.

Rockwell brings unexpected pathos to the difficult and problematic character of Dixon, the low-IQ cop out to prove himself without the smarts to achieve it. Does the film expect to have its cake and eat it with how it includes this blatant bigot before heading down a road resembling redemption for him? Perhaps. But it’s in the way that the film holds up the humanity and behaviour of its characters – adorned with scalpel-sharp wit, knife-twisting emotion and no real easy answers – that makes it such a compelling watch.