In a future where Earth has become a radioactive wasteland, 98% of the Human Population is concentrated in the Mega-Cities, where the law is enforced by the Judges, a police force entitled to act as jury, judge and executioner. The best Judge there is is Dredd (Karl Urban), who operates in Mega-City 1.
One day, Dredd is assigned to train recruit Judge Anderson (Olivia Thirlby), who had previously failed the Judge Academy, but received a second chance for being a mutant with heightned psychic abilities that might be useful. The duo is deployed to investigate a triple homicide in the block of Peach Trees, a violent area ruled by Madeline “Ma-Ma” Madrigal (Lena Headey), a sadistic drug dealer who has put a new substance in the market: Slow-Mo, a drug that alters its user’s brain’s chemics, making it appear as if time is in slow-motion.
Dredd and Anderson discover about Slow-Mo and raid one of the dealing points, capturing one of Ma-Ma’s men in the process. In order to prevent him from being taken to the Judges’ headquarters, where he’ll surely crack under interrogation, she has her skilled team of Hackers cut Peach Trees of the grid and activate the Nuclear Attack continency program, isolating Peach Trees inside a titanium dome. Ma-Ma then puts a bounty on Dredd’s and Anderson’s heads: Either they die, or the dome doesn’t get lifted.
Completelly stranded inside a hostile environment where everyone wants them death, Dredd and Anderson have to find a way to escape and put a stop to Ma-Ma’s plans before she is able to expand her turf over the other blocks, effectively becoming Mega-City 1’s number one drug dealer.