A young woman named Angela has been raped and murdered. After failing to hear from the local police department for seven months, grieving Missouri mother Mildred Hayes (Frances McDormand) hires a trio of billboards on a country road to shame the local sheriff Bill Willoughby (Woody Harrelson) into action. The billboards light up a storm of responses in the town, with results neither Mildred nor Willoughby could have anticipated.

Three Billboards Outside Ebbing, Missouri is the third feature film from the immensely talented writer/director Martin McDonagh. There is little point beating about the bush on this one: this is a bona fide film masterpiece. It is beautifully shot and paced, cleverly plotted, sparkles with dialogue and snark, and boasts some of the best screen performances I have seen in many a time. We may only be a week into the new year (this is a 2018 release here in Australia), but stupid as it sounds I think this is already a contender for the year’s best picture. At least, it is difficult to imagine too many films are likely to match it over the coming 12 months.

There are a number of specific reasons why Three Billboards works as effectively as it does. First and foremost there is McDonagh’s screenplay. It kicks off as a bleak comedy, and on that level it is tremendously effective and constantly laugh-out-loud funny. Then about half an hour McDonagh kicks you with a sudden and horrifying moment: it’s not violent, but it’s shocking and just pit-of-the-stomach awful to watch. In the moment the witty banter and the scabrous humour gets overrun by something very subtle and nuanced. Mildred and Willoughby stop being funny characters, and are pulled into sharp focus as actual people. The jokes keep coming – this is one of the funniest films I have seen in a long while – but they come from what feels like genuine and flawed human beings. That is a remarkable feat of screenwriting, direction and acting.

The plotting is sensational, because McDonagh refuses to make obvious choices. That makes it a difficult film to predict. Things do not go the way the audience expects them to, or possibly even wants them to. A mid-film event turns the entire movie on its head, in a fashion that feels like it should have been disastrous – but instead it throws everything into a whole new direction.

Frances McDormand dominates the film as Mildred Hayes. McDonagh gives her room to express Mildred as a multi-faceted and powerful character. Moments of hard-edged grit – which dominate the film’s trailers and advertisements – are balanced with scenes of tremendous vulnerability. McDormand sculpts a tremendous woman out of Mildred. I would be surprised if she is not drowning in awards within a few months: it is a performance that feels like a leading sentence in her eventual obituary.

The same goes for Sam Rockwell, who has always been an exceptional actor but is – like McDormand – gifted with a tremendously fascinating character. As the racist, ignorant police officer Jason Dixon, he should be immediately and overwhelmingly repellent. He isn’t. He does terrible things, and he pays a significant price for them, but by the end of the film there is an understanding of his personality and way of life that – while perhaps not likeable – is at least fundamentally understandable. He creates a fascinating, conflicted man out of what would in most other films be a caricature.

The film is rich with strong performances like these: notably Woody Harrelson’s harried Sheriff Willoughby, but also John Hawkes, Peter Dinklage, Sandy Martin, Kerry Condon, and the always underrated Željko Ivanek. One would be hard pressed to find a better cast in a film currently in cinemas.

Three Billboards is a striking and original masterpiece. It is that rare film that audiences are going to treasure for years to come.