'71. In 1971, a young British soldier named Gary Hook (Jack O'Connell) is sent to patrol the increasingly violent streets of Belfast, Northern Ireland. His first foray goes badly, when a street riot turns deadly and Hook is separated from his unit and left to survive the night in republican territory. Yann Demange's debut feature is a gritty 90-minute thriller set on a single chaotic night. Despite the specificity of its setting and time, it's essentially a lost-in-dangerous-territory set-up familiar from Western, war and crime films. Mostly, Hook is forced to react to the rapidly changing events around him, which include internecine struggles within the local paramilitary group, with the complication of undercover British forces complicit in corruption and collusion. The stuck-behind-enemy-lines part is an easier sell than the political drama, which might be confusing to those unfamiliar with this specific history and its nuances. Also getting a bit lost in the storytelling is '71's larger theme about the role of the soldier as a disposable pawn in ill-defined mission with an unclear chain of command. But this is a gripping outing, with O'Connell (last seen suffering endlessly in Unbroken) managing a nearly dialogue-free role, and a break-out performance by Corey McKinley, as take-charge child loyalist.