In the vast, post-apocalyptic metropolis of Mega City One on America's east coast, the only law is provided by the Judges of the Hall of Justice - cops with the power of judge, jury and executioner. Most feared among these law-keepers is the ruthless and implacable Judge Dredd ( Karl Urban). More and more of the inhabitants of Mega City One are addicted to a drug that alters the brain's perception of time: Slo-Mo. While assigned to train and evaluate Cadet Judge Cassandra Anderson ( Olivia Thirlby), Dredd is called to instigate a crime in Peach Trees, the notorious high-rise slum tower controlled by former prostitute-turned-drug-lord, Ma-Ma ( Lena Headey) and her clan. The Judges capture one of the clan's senior members and Ma-Ma locks down the tower, leaving Dredd and Anderson with a choice: escape the slum with their prisoner or climb to the top of the tower to capture Ma-Ma and judge her as well.