In a dystopian future where America has become a irradiated wasteland, the sprawling megacity known as Mega-City One is a violent metropolis where criminals rule the chaotic streets. The only force of order lies with the urban cops called "Judges," who possess the combined powers of judge, jury, and instant executioner. Among the most feared is the stoic Judge Dredd, who is tasked with evaluating the newest recruit, Cassandra Anderson, a rookie with powerful psychic abilities due to a genetic mutation. On what's supposed to be a routine day, Dredd and Anderson are called to investigate a brutal murder in Peach Trees, a 200-story slum tower controlled by the drug lord Ma-Ma and her clan.

Once inside Peach Trees, the situation escalates when Ma-Ma seals the building with a defensive system to prevent the Judges from leaving. Trapped inside the skyscraper, Dredd and Anderson must contend with the relentless onslaught of Ma-Ma's henchmen as they attempt to enforce the law and reach their target. Amidst the chaos, the duo uncovers the hub of Ma-Ma's empire, which is responsible for the production of a dangerous drug called Slo-Mo, which slows the user's perception of time. As they fight their way through adversaries and the complex realities of the judicial system in Mega-City One, both Dredd and the rookie Anderson are put to the ultimate test of their abilities and values.