The game is set on the planet Vega 4 in the city of New Shanghai. A work crew performing underground construction discovers a colony of Aliens which attack them and then quickly moved to the surface. The city is quickly overcome by the Aliens, but the citizens send out a distress signal to Earth which is also received by a passing Predator ship. The Predators decide to hunt the Aliens on Vega 4, seeing them as challenging prey. The player battles through six stages, fighting various types of Aliens and bosses. Many of the boss enemies are Aliens which have gestated in different types of animals and thus demonstrate characteristics of those animals. These include an aquatic Alien that emerges from a dolphin, a primate-like Alien gestated in an ape, a winged Alien gestated in a bat, and a snake-like Alien. After battling the Aliens on Vega 4 the player Predator travels to the Orion Nebula for the final stage and battles the Alien queen.