Upon hearing of several recent robberies of food delivery trucks in Mexico, Joyce Manning, Army officer Lt. Col. Glenn Manning's sister (though in The Amazing Colossal Man, his fiance said he had no surviving family), becomes convinced that her brother survived his fall from the Boulder Dam at the end of the first film. Along with Army officer Major Mark Baird and scientist Dr. Carmichael, she goes to Mexico to look for him.
It is discovered that Manning, now grown to 60 feet tall after being exposed to plutonium radiation, survived his fall from the Boulder Dam at the end of the previous movie, but he has gone insane and part of his face was left disfigured following his confrontation with the Army there, turning him into a zombie-like creature.
Manning is captured, drugged by the Army, taken back to America, but he again escapes and goes on a rampage through Los Angeles and Hollywood. Eventually, Joyce makes him come to his senses and realizing what he has done, he kills himself by electrocution on high-voltage power lines near the Griffith Observatory.
The sequel was featured in season 3, episode 19. Mike Nelson portrayed again the film's title character; opposed to his first encounter with Joel and the Bots, he shows more gentleness to them after seeing the transmission picked up by his "goofy dental work", but is still somewhat adamant when he tells them why Bert I. Gordon didn't pick him for the sequel.