The year is 20XX. A nuclear weapon combined with chemicals made by a mad scientist explodes in the city of New York, turning many of the city's inhabitants into savage mutants willing to obey any command. The scientist establishes an organization he calls "Big Valley," consisting of these mutants and many advanced military weapons. He orders them to take the ruined city by force and refuse to let anyone enter. Desperate, the US government hires the help of two super-powered mercenaries to enter the city and eliminate the villains occupying it.