On the trail of a lost cargo of illegal bio-weapons, Judge Dredd sets foot aboard the Cityship Sargasso, a vast, raft-like agglomeration of ancient toxic waste tankers loaded with stateless refugees from warzones around the world. The cityship's have become home to large populations of mutants and scavengers. So when the law comes on board, Dredd finds himself as an unwelcome guest - but so is the bio-weapon that is cutting a swathe through the ship's population.