Young Glenn Cameron (Alan Frost) finds a 50-foot cone sticking out of the ground near a small Illinois town. He reports his discovery, and the government sends a UFO committee, headed by Sen. Powers (Jack Hill) and scientist Dr. Paul Kettering (Edwin Nelson). Soon, they learn several townspeople have vanished, including Glenn's father, Mayor Cameron (Orville Sherman). But, when he returns, he is under the control of a mysterious creature attached to his brain, and an alien siege begins.