The serial-killer Hud Masters and his partner Logan have been recruited by a governmental agency to hunt down aliens that can survive for a period inhabiting human bodies. Logan reports their murders to her boss Frank Russo, a family man married with Stacy Russo with a daughter, who has a team to remove the bodies and any evidence. When an alien switch bodies to escape from Hud, Lt. Murcer, Lt. Clark and the coroner Santo are forced to return the bodies and Hud, who had been captured by the detectives, to Frank that explains that one hundred aliens from an evolved race had moved to Earth since their planet is doomed. Now Hud has to chase the dangerous Leader, who has adapted to the atmosphere of our planet and wants to breed.