Having lost his love Jane Foster to another man, Thor reacts by beating the living crap out of a file cabinet. Angered at how his Thor identity is messing up his life, Dr. Don Blake longs to confess his secret to Jane but he has been forbidden to by Odin. The All-Father, who has been watching his son’s antics from on high, summons Thor to Asgard and advises him to put all thoughts of Jane Foster from his mind, but Thor cannot. Don Blake makes the decision to travel far away….
In a small village in India, Don’s old friend Professor Shecktor is close to discovering an antidote for snakebite. His jealous assistant Klaus Voorhees plots a way he can gain the credit for himself. He plans to let a deadly cobra bite them both—and to cure only himself….
When Don arrives in India he hears the news that Professor Shecktor is dying. Changing into Thor he hurries to his friend’s side. There, he learns the truth from Shecktor (who doesn’t seem surprised to see a Norse god walk into his bedroom). The Professor reveals that the snake in question was radioactive and that as a result of that and the antidote Voorhees has gained cobra powers. Heading to the airport, Thor learns that Voorhees has boarded a plane for New York; the Thunder God calls up a typhoon to blow himself across the Ocean and catch up with his quarry. Voorhees, having adopted the costumed identity of The Cobra, enters a chemical plant and slithers along the ceiling and demands the executives mass-produce the serum for him to create an army of serpent men. Thor crashes through the window and confronts the villain, who fires cobra dart and cobra gas bombs at the hero. While Thor swings his hammer to blow the deadly gas out the window, the Cobra entangles him in an unbreakable Cobra-Cord, causing him to drop his hammer and the villain hurls Thor out of the window. After sixty seconds with his hammer, Thor transforms back into Don Blake, whose smaller form can easily escape his bonds. He rushes back inside and reclaims the hammer and again confronts his foe. Cobra unleashes a high-pressured stream of acid from a lab tank which slows Thor down briefly. Attacking his foe, the hero accidentally smashes a tank of chemicals which blinds him long enough for the villain to get away. Cobra flees to a random doctor’s office—which just happens to belong to Dr. Andrews, Jane’s new employer. The villain demands access to Andrews’ lab and the terrified medico readily agrees. Disgusted with his cowardly performance, Jane spies Thor flying past the window and hurls a flask through to attract his attention. For this act, the Cobra fires deadly darts at her but Thor intervenes just in time. The villain seizes Jane as a hostage and climbs out the window slithering down the wall; Thor flies around the building and hits Cobra by surprise. Jane is rescued but the Cobra gets away. Jane returns to work for Don, and the Cobra is left plotting further mischief.