A glowing, pulsating brain-like alien creature teleports to Earth and establishes a base in a cave on the beach near a U.S. military rocket launch site. It communicates telepathically with the children of the engineers and technicians involved in constructing and flying the latest in Cold War technology: an orbiting H-bomb platform to be launched atop a six-stage rocket. With 12-year-old Bud Brewster as "the leader" (he can immobilize people, prevent them from speaking, etc, with the blob's help), the kids start willingly doing the alien's bidding as the adults try to figure out what is happening.
The blob is powerful. When an enraged, drunken stepfather chasing after his wife's son prepares to assault the boy, the blob kills him. When technician Hank Johnson discovers the existence of the blob in the cave, his mind is "taken away" and he is hospitalized. When technician Dave Brewster tries to tell his bosses what is going on, his son Bud (who has walked through base security) shows up and prevents him from writing or speaking.
The blob is eventually able to communicate its message of peace and disarmament, and departs from Earth.
- Michel Ray as Bud Brewster
- Adam Williams as Dave Brewster
- Peggy Webber as Anne Brewster
- Jackie Coogan as Hank Johnson
- Russell Johnson as Joe Gamble
- Johnny Crawford as Ken Brewster
- Jimmy Ogg as Floor Manager