Description
The film opens with a green-skinned man (Franne Schacht) wandering aimlessly through the desert with a mysterious laser cannon attached to his arm. Nearby, an alien spacecraft lands and two reptilian creatures carrying weapons emerge. After a brief firefight, the aliens disintegrate the man, then return to their spacecraft and fly away, leaving behind the laser cannon and a metallic pendant the man was wearing. Elsewhere, teenager Billy Duncan (Kim Milford) wakes up in his bed, seemingly disturbed. He goes outside to find his mother (Janet Dey) has been invited to a trip to Acapulco and, despite her son's protests, she leaves her son behind. A dejected Billy goes to visit his girlfriend Kathy (Cheryl Smith), but her grandfather Colonel Farley (Keenan Wynn), a disheveled military veteran, spouts wild conspiracy theories and paranoid rants at Billy until he goes away. It becomes clear Billy despises the town he lives in and everybody around him, and for good reason; he is soon harassed both by a teenage bully named Chuck Boran (Mike Bobenko) and his nerdy friend Froggy (Eddie Deezen), and by two police deputies (Dennis Burkley and Barry Cutler), who give him a speeding ticket.
Billy wanders into the desert alone and discovers the laser cannon and pendant. He starts playing with the cannon, making "pow, pow, pow" noises and pretending to shoot things. However, while wearing the pendant and using the cannon simultaneously, the weapon actually fires, and Billy starts firing randomly at things in the desert. Meanwhile, on the alien spacecraft, the two aliens converse (in an unsubtitled alien language) with their leader, who orders them to return to Earth and recover the cannon: it is implied that the aliens left the cannon and pendant behind under the presumption that no other human would be able to use them as the green-skinned man had. Meanwhile, Billy and Kathy attend a pool party with other teens, where Chuck makes an unwanted advance on Kathy, resulting in Billy fighting with Chuck and Froggy. That night, from a hidden vantage point, Billy fires at Chuck's car with the laser cannon, resulting in a huge explosion that Chuck and Froggy barely escape. A government official named Tony Craig (Gianni Russo) arrives to investigate both the explosion and the desert where Billy found the cannon. Tony informs the local sheriff (Ron Masak) that the town must be sealed off due to his investigation.
Meanwhile, Billy feels sick due to an unusual growth on his chest. At Kathy's urging, he visits Doctor Mellon (Roddy McDowall), who surgically removes a metallic disc from Billy's chest. He calls the police laboratory technician Mike London (Rick Walters) to arrange for the disc to be investigated. However, later that night, a green-skinned and seemingly crazed Billy opens fire on Mellon's car, killing him in an explosion. The next day, Tony investigates the wreckage and recovers unusual material, which he brings to Mike London. After some experiments, Mike concludes it is an alien material and cannot be destroyed. Later that night, Billy, once again appearing deranged and grotesque, attacks and kills the two police deputies who harassed him earlier. Elsewhere, Billy and Kathy lay together outside next to Billy's van. While he is sleeping, Kathy discovers his alien pendant and puts it on Billy's chest, which turns his skin green and his eyes and teeth hideously deformed. Billy attacks the horrified Kathy, but she escapes.
Billy goes on a rampage, shooting things at random with the laser cannon. A small airplane with law enforcement officials opens fire on Billy, but he destroys the plane. Next, he comes across Chuck and Froggy and kills them by destroying their new car with the cannon. Meanwhile, Tony Craig questions Colonel Farley and Kathy about Billy, while elsewhere the two aliens land on Earth and begin searching for Billy themselves. After killing a hippie (Michael Bryar) and stealing his van, Billy travels to a city block where he fires indiscriminately at his surroundings, screaming like an animal. Kathy and Tony arrive in their car and find Billy in an alley. Before they can speak to him, however, one of the aliens shoots him from atop one of the nearby buildings. Billy is killed, the laser cannon and the pendant are destroyed and the alien departs in the spacecraft. The film ends with Kathy crying over Billy's corpse as Tony looks on.
