Plot

Through some harmless playacting, Dr. Smith unintentionally conjures up the magical gauntlets and war hammer of the Norse god Thor. Taking him for a mighty warrior, Brynhilda spirits Smith off to Asgard for a showdown with Thor.

Dr. Smith finds the magical hammer of Thor, who presently shows up, searching for his hammer, causing Smith to faint. Soon after, Smith fools around with Thor's magic items and finds himself in Niflheim, the realm of the evil elves, who taunt him while a dragon menaces him. Drawn by Dr. Smith's story, Will returns to the site and is abducted by Thor's wife, who is entranced with the boy and takes him to Thor's abode. Blaming Smith for Will's disappearance, John and Don convince him to rescue Will, requiring an intricate plot whereby Smith masquerades as a princess and--by squeezing water from a sponge crafted to look like a potato--defeats a drunken Thor in a contest of strength. Convinced that he has lost his strength, Thor backs out of a forthcoming battle with the frost giants. Given a stirring speech by Will, Thor defeats the frost giants and returns him and Smith to the Robinsons' landing site.