A virus outbreak has turned most of the population into zombies. The survivors built a massive wall around the city and have been living inside it since. Alex, a researcher who made it inside the wall, has uncovered the truth: the virus was a human creation, a laboratory accident that occurred during the development of a therapeutic drug. The government covered it up. Alex goes public with what he knows. Nobody believes him. The government has him thrown outside the wall, into the zombie-infested territory, as a dangerous agitator. Alex, standing in that territory, decides the only appropriate response is revenge.