''71' a chilling tale of a man's attempt to survive a wartorn night

The early 1970s were bloody in Northern Ireland, with the Troubles building toward a fever pitch of bombings, riots and shootings that sent the death toll skyrocketing. It makes for an explosive backdrop in "'71," director Yann Demange's gripping feature directorial debut about a British soldier who gets left behind by his unit in Belfast following a chaotic riot in 1971.

The plot sounds like the low-hanging fruit of action movies: A hero in peril needs to survive the night. But the complicated history elevates the story above pulp.

Up-and-coming actor Jack O'Connell ("Unbroken") plays Gary Hook, who joined the army after growing up in an orphanage where his younger brother still lives. Shortly after Gary enlists, his unit is shipped to Belfast to subdue an increasingly dangerous situation. If the newbies in Gary's unit are ill-prepared, then their commander, the friendly if nervous Lt. Armitage (Sam Reid), is even more naive. He sends the men into the thick of things without riot gear, hoping a human touch and eye contact will be enough to quell the violence. It isn't.

The city looks apocalyptic with burned-out, still smoldering cars; small children hurling grotesque insults (and worse); and, at the sight of soldiers, people slamming metal trash can lids against the street, creating an unbearable din.

During the first of many harrowing scenes, Gary gets separated from his unit and beaten by a mob. By the time he breaks free, his fellow soldiers have already rolled out, forcing him to scurry through the foreign streets, trying to evade armed nationalists out for British blood.

Unbeknownst to him, Gary's survival depends not just on his own instincts, but on a complicated web of people, including two factions of the Irish Republican Army, British loyalists and undercover agents. To add to the confusion, each group is double-crossing another.

Meanwhile, Gary continues his odyssey and meets some charitable souls along the way. A young child (whose accent was indecipherable to these American ears) leads the soldier to what seems like safety, while a father and daughter risk their lives to help the young man.

The taut script was penned by Gregory Burke, who wrote the acclaimed play "Black Watch," about Scottish soldiers in Iraq. The man knows how to build a story: Every early scene has a job that it performs well, to either deepen our understanding of the protagonist or foreshadow what's to come.

The filmmaking is equally efficient. After an explosion, the picture blurs and the only sound is a dull ringing. We feel like we're there. But be warned: The fact that Demange aims for realism means the violence can be grisly.

"'71" succeeds as an action thriller, but with enough complexity to keep the brain engaged. The film is also a reminder of the byproducts of hatred. Seeing children who were taught from a young age to despise is both painful and powerful. The Troubles are over, which should give the viewer a tiny glimmer of hope. With all the difficult images in " '71," though, neither Burke nor Demange seems particularly interested in optimism.