The Knife is a quietly devastating procedural and psychological drama set entirely inside or around a house on one terrible night. Director and co-writer Nnamdi Asomugha doesn’t hold back with this taut tale that turns a family’s life upside-down in an instant, and has a lot to say about the state of the nation. Intense and thought-provoking, it’s a brilliantly filmed, unsettling watch.

On an otherwise quiet night in their new house, construction worker and father of three Chris (also Asomugha) works on a room before heading to bed in the early hours. A noise wakes him, and he finds a strange woman in his kitchen. By the time his wife, Alexandra (Aja Naomi King), and two of his children find him, having been woken by the noise, they see the woman unconscious, possibly dead on the floor, a knife near her hand and Chris standing over her.

 The police soon arrive in response to Chris’s call, including seasoned officer Detective Carlsen (Melissa Leo), who splits up the family, adults and children to take their account of what happened, convinced she’ll uncover the truth.

 Asomugha, a one-time professional football cornerback, actor, and producer, makes a confident directorial debut with a film determined to challenge its audience, primarily by what it doesn’t say. His debut is all the more impressive, with close camera work making the most of the house’s architecture and essential to getting inside the characters’ heads, given he’s at the centre of the drama playing the unfortunate father.

 In some ways, The Knife’s atmospheric but lean screenplay suggests a whodunnit, confronting viewers with a choice: Did the father injure the woman in self-defence when she came at him with a knife or not? We’re handed more information than the police but know less than the father in this balancing act—while the knife of the title is important, Asomugha’s clever distribution of fact, perception, secrets and interaction leaves us in no doubt that the significant factors impinging on the night aren’t inside the house at all. Still, the variables stack up, ready to tug on when an inspector calls…

 Leo’s disarming detective is a fascinating creation. As she quietly works through the facts and her witnesses, viewers will likely find themselves agreeing with and disagreeing with her various actions. That grey shadow falls over all the characters, played by a universally excellent cast. The core family is brilliantly sketched through scenes where small secrets and revelations from the past pop between them, particularly the parents: The father, a construction worker on prescription medication; the mother, who’ll do anything to protect her husband as a black man in America caught up in a shock crime. The naive simplicity of one daughter’s belief that all her father has to do is tell the truth becomes an almost unbearable source of tension.

 Despite its tight, domestic setting, The Knife is many things—a siege, an interrogation, a psychological and sociological examination and a philosophical touchpaper. To wrap it up, it ends with a factual summary of the events being put on the record as we stare into an unspeaking face—possibly the greatest display of silent emotions to close a film since final scene of The Long Good Friday.