In this pulp science-fiction film, a flying saucer full of aliens of a "Superior Race" lands on Earth, searching for grazing grounds for their Gargon cattle. One of the aliens uses a ray gun to kill a curious dog ("They blast the flesh off humans!"). Rebellious Derek inspects Sparky's dog tag and realizes that civilized beings inhabit the planet. He begs his companions to consider the rights of the people of Earth, but the other crewmen turn on him. They leave one of the lobster-like Gargon chained inside of a cave, make responsible Thor hunt down the escaping Derek, and return to their home planet to fetch herds of Gargon.
While Derek befriends Betty, Gramps, and Joe in the nearest suburban utopia, Thor's relentless manhunt results in numerous blasted skeletons and abductions. The fun really gets going when the now gigantic Gargon escapes its chains and goes on a murderous rampage. Spunky Betty begins a romance with Derek, who promises to make Earth his home. Reporter Joe is hot on the trail of the double-murder story that grows into something really big.Teenagers from Outer Space sports primitive special effects and almost-bad acting, but really they just add to the angsty fun of this 1959 flick.