It started out as a relatively quiet day at the CityVille Police Station. Deputy Strong and his team had successfully cracked down on a couple troublemakers. Nothing so dangerous that the wife and kids at home would have to worry, but not so smooth that you didn't feel you deserved a nice jelly-filled from the daily donut drop when all was said and done. When they picked up a high-school teenager drooling outside the advanced organic chemistry class, Deputy Strong and Chief Zito thought it was just another case of a kid clownin' around on school time. Turns out the kid was infected with a zombie virus created by the evil Dr. Mayhem as part of his plan to take over the city! After snacking on his cellmate and chomping on the Chief, the kid had turned two more citizens into zombies - and that's when the rampage began. Now the zombies are on the loose and on the attack. Dr. Mayhem's evil plan is working. You have to defend your city from invasion.