Curious adolescent boy David MacLean (Jimmy Hunt) confronts aliens who have set up base in his backyard. The extraterrestrials intend to use mind control on the local townsfolk. Determined to stop the invaders, who have already co-opted his father (Leif Erickson), he attempts to warn others. But when local law officers also succumb, David teams up with astronomer Stuart Kelston (Arthur Franz) and Dr. Pat Blake (Helena Carter), and the trio must fight together to repel the insidious intruders.