Robert Miller (Toby Kebbell), a veteran soldier, is returning from the war in Afghanistan to his home in a violent decaying South London council housing estate, overrun by gun-toting youth gangs. The gangs are led by a drug lord gangster (Ashley Thomas), who is interested in Miller working for him. His job offer is rejected.
Through an ex-army mate (Tom Brooke), Miller finds work in undercover surveillance. He is soon recruited by a couple of shady government operatives (Tony Curran and Brian Cox) for an undercover operation to keep tabs on a network of suspected terrorist cells. Embedded in the terrorist group is a Lebanese-born British citizen informant (Adi Bielski).
Miller soon discovers that the security forces and the intelligence...