The New Zealand Astro Investigation and Defence Service (AIDS) dispatches a team comprising Derek, Frank, Ozzy, and Barry to uncover the mystery behind the sudden disappearance of the townsfolk in Kaihoro, located on the North Island of New Zealand. Upon their arrival, they quickly discover that the town is infested with space aliens masquerading as humans. In a shocking turn of events, Barry manages to eliminate one of the aliens, only to be besieged by a gang of others armed with sledgehammers.
As Derek alerts Frank and Ozzy, who are en route to Kaihoro, he resorts to torturing Robert, an alien they had previously captured. The screams of Robert attract more aliens to their location. In a dramatic confrontation, Derek dispatches the reinforcements, but Robert turns against him, causing Derek to tragically tumble over a cliff, seemingly meeting his end.
Meanwhile, Giles, a charity bill collector, inadvertently wanders into Kaihoro, where he is attacked by Robert, who has been feasting on the brains of the alien that Barry killed. In a desperate bid for safety, Giles flees in his car and seeks assistance at a nearby residence. Unfortunately, he is captured by another alien—disguised as a chef—who renders him unconscious with a wooden meat tenderizer mallet. Giles later regains consciousness in a bathtub full of water, where he learns that he is on the menu for a terrifying feast.
Simultaneously, Derek surprisingly awakens in a seagull's nest. Realizing that part of his brain is leaking from the back of his head, he humorously juggles the situation by stuffing it back in and securing it with a hat.
As night descends, Frank, Ozzy, and Barry stealthily infiltrate the aliens' lair, discovering a sinister chamber teeming with bloody cardboard boxes. They manage to capture and kill an alien, after which Frank dons its shirt to blend in at an alien gathering. There, he uncovers the horrifying truth: the residents of Kaihoro have been harvested as part of an alien fast food chain named 'Crum's Country Delights'. In a particularly grotesque moment, Robert vomits into a bowl that the aliens consume from, with a horrified Frank among them. He eventually escapes to relay this disturbing information to his comrades, who plot to rescue Giles while the aliens slumber.
At dawn, their escape attempt goes awry when the aliens attack them, igniting a fierce and explosive gun battle where both sides unleash chaos. Derek joins the fray, only to have his hat shot off, leading him to lose more of his brain. Resourcefully, he fashions a headband from his belt, seizes a chainsaw from his car, and charges toward the alien base. As they make their escape with Giles, they encounter the formidable alien leader, Lord Crumb, who reveals his true form and pursues them.
In the chaos, Ozzy detonates Frank's car, overrun with aliens, using a rocket launcher. Frank and Ozzy return to confront Lord Crumb, taking down numerous aliens along the route. In an intense showdown, Derek, now wielding his chainsaw, kills an alien that was about to shoot Frank and Ozzy, astonishing them with his survival.
As they attempt to flee, Lord Crumb shoots Ozzy in both legs, while Frank's rocket fire goes awry, nearly hitting Derek instead and ultimately obliterating a sheep in a nearby field. In a climactic twist, Derek is knocked out by Lord Crumb, who reveals the aliens' base is a colossal spaceship launching into the cosmos — with Derek inadvertently aboard.
Inside the ship, Derek gazes out the window, witnessing Earth shrink away. Suddenly, a loud commotion captures Lord Crumb's attention, allowing Derek to launch a surprise attack, slicing the alien in half with his chainsaw. In a triumphant moment, he declares into his phone: > "I'm born again! I'm coming to get you bastards!" He then puts on the skin of the alien leader, laughing maniacally as he propels himself toward the alien planet with only his chainsaw in hand, undoubtedly intent on annihilating the alien race.
The film concludes with a heartwarming scene of Frank, Ozzy, Giles, and Barry driving into the sunset in Derek's car, leaving behind the chaos of Kaihoro.
