In the near future, America has been reduced to an irradiated wasteland and more than 400 million people are crammed into Mega City One on the eastern seaboard, which is patrolled by law-makers called Judges.
The Chief Judge (Rakie Ayola) asks universally feared Judge Dredd (Karl Urban) to assess rookie Cassandra Anderson (Olivia Thirlby), a mutant with devastating psychic powers.
Reluctantly, Dredd mentors Anderson and they head to the Peach Trees mega-block, home to 60,000 impoverished denizens, to investigate reports of a triple homicide.
The Judges apprehend Kay (Wood Harris) for the murders and, using her abilities, Anderson surmises that the suspect is linked to sadistic dealer Ma-Ma (Lena Headey).
Before Dredd and his protegee can interrogate Kay, Ma-Ma locks down Peach Trees and orders the hoodlums and lowlifes in the building to kill the interlopers.