A nuclear scientist who defected to the U.S. was exposed to nuclear radiation and has only a short time to live has been living in the desert. But agents from his country try to get him to return. Superman stops them but knows there's another agent whom they only by a code number will try to get him. When Clark tells Jimmy and Lois about him they go to see him and because they came in contact with him, they're exposed to the radiation. They decide to flee not knowing they're going into an area where a nuclear device is to be detonated.
A prospector who has hit it rich donates a silver mine to needy children and names it the "Superman Silver Mine." A crook, who bears a strong resemblance to the prospector, abducts him. The prospector refuses to disclose the location of the mine. Lois Lane and Jimmy Olsen are imprisoned while investigating. The crook has a metal plate in his head and Clark uses this fact (and his X-Ray vision) to figure out what's going on. Now, it's up to Superman to bring the criminals to justice and free the prisoners.
Professor Pepperwinkle creates a robot whom he calls Mr. McTavish. It isn't long before Jimmy and Lois learn about him and Pepperwinkle shows him to them. Later Superman shows up but as he is approaching McTavish he starts to feel weak so he leaves. That's when they learn that McTavish placed a meteorite in McTavish which they deduce is kryptonite. Some men who want to blow up the planet for a story they did, decides to use McTavish to assemble the bomb so they take him along with Lois and Jimmy. So Superman and Pepperwinkle have to try and find them.
Perry gets a wire from Lois, who's in Mexico, that she has discovered a donkey with psychic powers. Perry sends Clark down to investigate, and discovers that not only does the "burro" have psychic powers, but it has figured out Clark's secret identity as Superman.'
A criminal who was sent to prison by Superman and the Planet staff goes to the Planet office and tells them of his intention to go after them. They respond that Superman will stop him. Only problem is that he wears a lead mask to conceal his identity and he has other men wearing the same mask. Eventually he captures all of the Planet staff and puts them in a perilous situation and Superman has but minutes to save each one of them.