The film picks up immediately after the events of Alien vs. Predator. The Predator ('Scar'), who was impregnated by a face hugger before being killed by an Alien Queen at the end of the first film, gives birth to a Predalien on board his clan's ship, which then sneaks aboard a scout craft headed for Earth and runs amok. As the Predalien rampages through the ship, a Predator attempts to kill it with his plasma caster and inadvertently shoots a hole through the ship's hull, causing it to crash in the forests outside of Gunnison, Colorado. The ship's crew die either upon the crash or by the Predalien, which escapes. A boy and his father who are deer hunting see the crash and go to check it out. Both of them come across the wreckage of the ship-on board, and several facehuggers escape from the damaged containment tubes and quickly impregnate them both. Meanwhile, ex-con Dallas Howard (Steven Pasquale) has returned to Gunnison after time served in prison. He is greeted by his best friend and the town's sheriff Eddie Morales (John Ortiz). Ricky Howard (Johnny Lewis), who is Dallas' brother, delivers a pizza to his love interest Jesse; a fight between him and her boyfriend, Dale Collins, causes him to lose the keys to his truck, forcing Rick and Dallas to look for them in the sewers. Ricky catches sight of a chestburster, and both leave rattled after hearing a series of hissing and screeching. At this point, the hunting pair give birth to their chestbursters, and a few more facehuggers impregnate several homeless people in the sewers. Kelly O'Brien (Reiko Aylesworth) comes home after serving her time in the Marines, to an estranged daughter and waiting husband. Elsewhere, a distress signal sent by one of the dying predators reaches one of the Predator homeworlds, contacting a veteran hunter, (identified in the credits as "Wolf"). He arrives on Earth hours later to eliminate the Xenomorphs and destroy any evidence of the incident, while the community searches in earnest for the father/son hunting pair. At this point, Wolf has used a vial of corrosive liquid to remove all traces of the pair. One of the officers looking for the pair comes across the Predator, but is quickly tracked down and killed; he is skinned and found the next morning by Sheriff Morales. After a brief fight in which Wolf encounters the new Predalien (apparently the dominant alien of the infestation), the aliens spread throughout the city through a hole in the sewers leading up into the streets, starting a rampage that eventually leads to the destruction of the power plant and forcing the city into darkness. After barely escaping with their lives, Ricky, Jesse, and Dale manage to meet up with Eddie and Dallas. They head to a sporting shop, contacting the incoming National Guard; within minutes the entire force is decimated. Kelly, having lost her husband and barely escaping a Xenomorph, arrives with her daughter Molly. They are forced to flee when the Predator arrives, attempting to destroy as many aliens as he can; his plasmacasters are damaged, and he is forced to use them as a makeshift pistol. Unfortunately, Dale is killed when a dead Xenomorph's acidic blood melts his face off in the sporting shop. Meanwhile, as the small group attempts to escape the city, they are contacted by Colonel Stevens, who radios that air evacuation will arrive at the town's center within a half-hour. Kelly is unconvinced, believing that they will bomb the center of town for the best effect at both destroying and covering up the infestation. Eddie breaks from the group to join a small collection of fighting survivors who plan to wait at the center of town, while the remainder of them make for the hospital, where a helicopter is known to be. Unknown to them, the hospital has already been attacked and has become a hive for the infestation. When the group comes under attack, Jesse flees, unwittingly running into the path of Wolf's shuriken and brutally killed as a result. Rick attacks the Predator, causing it to lose the plasma pistol it was wielding. Rick is then impaled with a Xenomorph's tail, but manages to stay alive. Dallas picks up the energy weapon as the group continues towards the helipad, chased by the hostile hive. On the roof, Dallas stays behind briefly to fight off their pursuers with the plasma pistol, until he is cornered by an alien. Wolf appears only a moment later to brawl against the creature, allowing Dallas to escape, just as the Predalien arrives and attacks Wolf. As the two extraterrestrials battle, the helicopter lifts off, carrying an injured Ricky, Dallas, Kelly and her daughter, just as the air force arrives. The two creatures mortally wound each other, just as a nuclear device lands in the middle of town, killing the remaining survivors and destroying the infestation, but also causing the chopper to lose control and crash land in a clearing. Dallas wakes to find Kelly, Molly and Rick still alive and outside the crashed craft. After hearing threatening noises, they find themselves surrounded by camouflaged soldiers. Dallas gives up the plasma pistol, while med-evac tends to his still injured brother- Kelly reassures her daughter that the monsters are finally gone. The scene shifts elsewhere, to a corporate building in the US, where Colonel Stevens approaches an Asian female. He opens his briefcase, revealing the plasma caster. The woman, Ms. Yutani (of the future corporation Weyland-Yutani), states that the world is not ready for the new technology, but Colonel Stevens replies that the technology is not for our world, (but apparently for use in outer space, hinting at a sequel set in the future).