Slum is the villain from Mutation Nation. A mad scientist, he was shut down for conducting illegal experiments. Soon after, his lab exploded, and he disappeared mysteriously. Years after the incident, his experiments were forgotten and buildings were erected in the place were his lab was. Two police officers, who had been on vacation, return to the city, only to find that everyone was gone and that the city was now populated by weird mutants. Without options, the two take upon themselves to face the mutants and find the culprit, before the mutants spread through the entire nation and maybe the world. After crossing the street and defeating many mutants, they discover that Slum is still alive, and that he was the one responsible for turning people into mutants. The two head to the building located in the place of Slum's lab, where they find Slum, who turns himself into a horrendous mutant. They manage to kill Slum and escape the collapsing building.