Radiation from the sun is causing Bruce Banner to change into the Hulk without provocation. Rick Jones manages to lure the Hulk into a specially designed cave to hold him, but just then Doctor Octopus attacks General Ross' army base intend on stealing the powerful Kerium 99 from the lab.
Rio tells Bruce Banner about an ancient tribe in Yucatan that might hold a cure to get rid of the Hulk once and for all. Meanwhile the evil Spy Master is planning to steal the experimental Sonar Chrystalizer weapon that is being tested at General Ross' Army Base.
Bruce Banner has developed a powerful Gama Bomb, but just as it is about to be tested, a teenager named Rick Jones carelessly drives onto the testing ground. Banner manages to save Rick, but is bombarded by Gama rays himself thanks to a traitorous assistant. Although Banner survives the radiation, his body transforms into a giant green hulk as soon as he becomes angry.
Bruce and Betty are in Paris where he is speaking on a scientific conference and she is carrying the key to a secret gold vault. An evil descendant of the hunchback of Notre Dame kidnaps Betty to obtain the gold and leads the Hulk on a chase all over Paris.
Dr. Donovan has invented Cyclops, the most powerful computer on Earth to safeguard the entire military defenses of the United States. But Cyclops soon begins to think of itself as superior to human beings and, having discovered the real identity of the Hulk, plans to take over the world.
General Ross orders Bruce and Betty to use the Garth 7 computer to find out where the Hulk comes from and Major Talbot to head a team of Hulkbusters. Meanwhile, the evil Puppet Master is taking over Mesa City by mind controlling every citizen with his puppets. He's also made a clay figure of the Hulk to use as part of his master plan.
Banner hopes to use a newly invented Time Projector to travel back in time and prevent himself from becoming the Hulk. But the Hulk accidentally causes the entire visiting party, including Rick, Betty, Maj. Talbot and General Ross to travel a million years back in time.
The selfish Dr. Proto drains power from his colleague Bruce Banner's experiments to create a new life form. The organism, a yellow slime, soon begins to grow and proves to be unstoppable, possible even for the Hulk.
While experimenting with a gamma ray emitter, Bruce Banner is accidentally reduced to one inch in size. Meanwhile, Major Ned Talbot is in charge of the testing of the new T-70 tank, which is being targeted by saboteurs.
Rita is kidnapped at a stunt-bike show by the leader of biker gang The Screaming Vultures. They take her to their Leader, who has equipped them with futuristic enhancements (to both their bikes and their bodies) so they can steal a shipment of Vibranium for him. Bruce, Betty and Rick all stumble into the Leaders hands, who proceeds to use his Psychic Nullifier on Betty and Bruce.
Still on the run, Bruce Banner and Rick Jones arrive in Los Angeles, California to see if Bruce's cousin Jennifer Walters can help Bruce find a cure. When they find her Rick discovers that Jennifer is actually the She-Hulk thanks to a past blood transfusion Bruce gave her in order to save her life. Unlike the Hulk though, She-Hulk still keeps her intelligence after turning green, and uses those smarts to stop the Supreme Hydra from taking over Los Angeles.
Bruce Banner is testing a new Transmat beam but unexpectedly turns into the Hulk. When he arrives on the other side, Betty Ross witnesses the Hulk destroy the machine and thinks that by doing so, Banner is disintegrated. She becomes resolved to capture the Hulk, at first out of grief, but later because she thinks that by reversing the process, Bruce might still somehow be restored.