Driven by guilt for being unable to free his wife from a fiery car crash, Dr. David Banner (Bill Bixby) researches documented cases of everyday people who exhibited superhuman strength during times of great stress. He learns that peaks in solar gamma ray activity caused each of the cases; his inability to save his wife, despite his panic and rage, happened during a solar low. Convinced that high gamma is the key, David tries to artificially tap his own hidden strength but unknowingly takes a mega-overdose of gamma. Now whenever he is stressed, you know what happens. The mysterious "hulk" is pursued by reporter Jack McGee, who finally catches up to David as he and Dr. Elaina Marks try to find a cure. McGee accidentally sets off an explosion that proves fatal to Elaina. Triggered, the Hulk carries her to safety but weeps as she dies in his arms.
The epilogue shows David, assumed to have also been killed in the blast, visiting Elaina's grave. The Hulk is believed responsible for both Marks' death and his own, so David goes on the run, trying to stay one step ahead of the relentless McGee as he searches for a way to rid himself of the monster he created. The melancholy piano theme plays as David walks away into the distance.