Season 1 - Episode 1. First aired on Wednesday, April 5th 1978.
(also released as "Spider-man Strikes Back")
Read the full plot.
Peter Parker joins a group of his fellow students in protesting about the building of a nuclear reactor on the ground of his college. The students are concerned that the plutonium by-product of the nuclear reaction could fall into the wrong hands and an atomic bomb constructed.
While this is happening, reporter Gail Hoffman arrives in New York to interview Spider-Man. In order to make their point the students steal some plutonium from the lab. Spider-Man appears on the scene in an unsuccessful attempt to prevent the theft. But Spidey is spotted by security guards and is naturally blamed for the theft.
Meanwhile, in Switzerland, villain Mr White reads a newspaper report of the theft and deduces that it was the students rather than Spider-man who stole the radioactive material. He plans to relieve the students of their ill-gotten gains. He departs immediately for the United States with his monstrous henchman, Angel. White kidnaps Peter Parker, a known associate of Spider-man in an effort to locate the plutonium.
When one of the students involved in the theft is admitted to hospital with radiation poisoning, Peter changes to Spider-Man to track down the plutonium. But White and Angel get there first. In the ensuing
fight, Spidey is hurled off a twelve story building and plunges earthward, seemingly to his death...
[Summary from UK 1982 Spider-man Annual]