The world is shocked by the appearance of three talking chimpanzees, who arrived mysteriously in a spacecraft. Intrigued by their intelligence, humans use them for research - until the apes attempt to escape.

Three bounty hunters from space fly back to the town of Grovers Bend, hoping to save local residents from a new batch of Critter eggs.

A representative of an alien race that went through drastic evolution to survive its own climate change, Klaatu comes to Earth to assess whether humanity can prevent the environmental damage they have inflicted on their own planet. When barred from speaking to the United Nations, he decides humankind shall be exterminated so the planet...

A spaceship is sent to Mars after an alien distress signal is picked up. They find one survivor, but when a crew member is found drained of blood it's evident they have rescued a bloodsucking monster. (Uses footage from Encounter in Space (1963).)

An oceanic observation station is in desperate trouble after a sudden shark attack wrecked the oxygen supply. The accompanying ship, a coast guard cruiser, and other ships in and around the Bermuda triangle are attacked as well. The US Navy sends a submarine to investigate, but soon they too are under attack.