On the Lunar Base 4 Correctional Facility, convict Adrian Dunn (Billy Drago) gets into an altercation with another prisoner over a cigarette. After Dunn kills him something bursts from the corpse's face, landing in a wound in Dunn's arm and apparently causing his deaht. The body is shipped back to his hometown of Boston for an autopsy. En route Dunn revives, breaks out of the spaceport, and wanders the city raping women at random and infecting them with a virus thatg causes the infected to breathe out methane. Black Shield cop Cameron Grayson (Roddy Piper) takes the case of tracking down Dunn, eventually leading to the discovery that the virus was bio-engineered by aliens to terraform our world into a suitable habitat for them. Grayson must stop both Dunn and the virus before the entire planet becomes the enw home for a domineering alien race.