In an act of biological terrorism, a trio of aliens try to poison the ventilation system of a suburban shopping mall. When their plan fails, one of the aliens is forced to abandon his body and take over the body of a pregnant woman named Nancy Salvo. However, the violence of the absorption proves too much for Nancy's body, which promptly goes into labor. While Nancy is rushed to the hospital, the two remaining invaders follow the ambulance to retrieve their comrade -- and the baby she is about to deliver!