 Colonel Glenn Manning's sister, becomes convinced that her brother (Dean Parkin) survived his fall from the Boulder Dam (as seen in "The Amazing Colossal Man").Along with Army officer Major Mark Baird (Roger Pace) and scientist Dr. Carmichael (Russ Bender), Joyce goes to Mexico to look for Glenn and finds that he has, in fact, survived, but was left disfigured and nearly mindless by the trauma of his fall.Manning is eventually captured, drugged by the Army, and transported back to the United States.