In the midst of the riots that left parts of the Michigan city capital ablaze in 1967, three cops barge their way into a low-rent hotel and terrorise the largely black guests inside. They’re ostensibly looking for someone who fired shots out of a top-storey window – actually a prank involving a starting pistol – but in reality, this is a pretext for a sadistic, racially-motivated bout of violence, intimidation and ultimately murder. Shot in a grainy, handheld style that dovetails with the news reports and still images Bigelow intercuts with her own footage, Detroit follows the movements of those involved in the incident at the Algiers Hotel. As the police and National Guard make brutal attempts to restore control across the city, a young singer, Larry (Algee Smith) and his best friend Aubrey (Nathan Davis Jr) are forced to seek refuge in an $11-per-night room at the Algiers. Only a few yards away, security guard Melvin Dismukes (John Boyega) is standing sentry at a grocery store for the night. When shots ring out from the nearby hotel, and a group of soldiers from the National Guard head over to investigate. There, Melvin encounters Krauss (Will Poulter), a Detroit officer who has no problem with shooting unarmed, fleeing looters in the back. Along with two other cops, Demens (Jack Reynor) and Flynn (Ben O’Toole), Krauss begins to search the building – and, as they drag its residents out of their rooms one by one, the depth of his racism – and possibly psychosis – is revealed. Unflinchingly, Detroit paints an ugly portrait of a country divided by racism and normalised violence. Aided by Barry Ackroyd’s intimate cinematography, Bigelow’s film immerses the viewer so fully in the experiences of its African American protagonists that the sense of oppression and fear radiates from the screen. Beyond the toe-curling scenes at the film’s centre, there are also the quieter but no less disturbing moments of racism – the contemptuous glances, the subtly demeaning aside from a cop or a lawyer. Bigelow captures all of this through her superbly understated style of filmmaking. The performances are similarly natural and raw, from Will Poulter’s renegade officer – who seems to have an internal rationalisation for everything he does, no matter how  despicable – to John Boyega’s quietly outraged security guard. Towering over everyone else, however, is relative newcomer Algee Smith; as a smiling, optimistic soul singer with dreams of stardom, his character arc is the most poignant of all. Detroit is an assaultive, harrowing film, and at times difficult to watch, but it’s also heartfelt and urgent.  It is, quite possibly, Kathryn Bigelow’s masterpiece. Detroit is out in UK cinemas from the 25th August.