It has been nearly a year since the appalling rape and murder of Angela Hayes, and her mother Mildred (McDormand) is incensed by the lack progress in bringing her daughter’s killer to justice.

Taking matters into her own hands, Mildred rents three billboards on a little-used road outside the small township of Ebbing and plasters them with a message designed to shame the local chief of police, Willoughby (Woody Harrelson), into action.

Her action galvanises the town but not in quite the way she anticipated. Willoughby attempts to explain the stalled investigation and his frustration with the lack of evidence, but Mildred is implacable. Even the revelation of Willoughby’s terminal cancer will not soften her grim drive for justice.

The locals are outraged on behalf of their beloved Chief Willoughby and various characters rally to his defence in increasingly violent ways. Most noteworthy of the chief’s allies is Officer Dixon, whose racism, violence and vocational ineptitude is played with a brilliant lack of dignity by Sam Rockwell.

Writer and director Martin McDonagh is in top form, surpassing even his brilliant work on In Bruges (2008). His skill as a playwright is evident in the film’s rapid-fire dialogue and brilliant monologues, while his use of the stage’s standard three-act structure lends the film the gravitas and momentum of a classic tragedy.

Comedy and scenes of dramatic power are artfully counter-posed. McDonagh’s use of black humour to leaven an otherwise grim tale of vengeful wrath is realised in such a way that it deftly underscores the grief of Angela’s family and the decisions made by Chief Willoughby as he struggles to come to decisions that have heartbreaking ramifications.

The audience is teased with the promise of a resolution but left with a far more morally complex conclusion.

Shot in North Carolina by cinematographer Ben Davis, the film captures small-town America without tipping into sentimentality, It is distinctly American, yet for all the violence and roughness, there is a clear-eyed compassion.

Three Billboards Outside Ebbing, Missouri is a difficult film to classify, containing elements of tragedy, comedy and a morality tale with no character left unaffected by the many turns of the plot.

Even if your interest is not piqued by the story, the performances alone – especially that by McDormand as the flawed and furious protagonist – make it worth your time. McDormand can claim this as one of her best, alongside her roles in Fargo and Olive Kitteridge.  Harrelson plays to his considerable strengths, and Rockwell is stunning as he transforms a thoroughly unlikeable redneck into a character inspiring considerable compassion.

Three Billboards Outside Ebbing, Missouri is a harrowing and highly original meditation on grief and rage.

At yesterday’s Golden Globes, Three Billboards Outside Ebbing, Missouri won multiple awards, including for Best Motion Picture – Drama, Best Actress in a Motion Picture – Drama (Frances McDormand), Best Screenplay (Martin McDonough) and Best Supporting Actor (Sam Rockwell).