After Dudley does a magic show for the Marvel Family, Mary and Dudley head on the way to a Magician Convention in an airplane, and while en route, Mary Batson and Uncle Dudley find themselves caught in a time warp that resembles a tornado. They are then transported to the fourth dimension, where they are located by a giant young girl named Magna, who wants to play with them like dolls.
Meanwhile, Billy Batson and Freddy Freeman learn of Mary and Dudley's disappearance, and their investigation leads them to determine that they fell through a time warp. They then fly faster than the speed of light, so that they can create a time warp and enter the fourth dimension. Upon arrival, they realize that they no longer have their super powers. And they are then attacked by a giant Laser beast.
Meanwhile, Mary and Dudley are incarcerated at an unknown location. The door to the cell opens, and some sort of Reptile man opens up the door, and he tosses Doctor Sivana into the cell with them. He is bound, and Mary, who doesn't know who he is, unties him, since she lost her memory. He then draws his shrinking ray gun he shoots at them, but since everything is reversed in the fourth dimension, the ray didn't shrink Mary and Dudley, instead, it made Sivana grow. He is so big that he crashes through the ceiling. The falling debris injures Mary's head, but it also allows her memory to return.
Sivana goes out to find Billy and Freddy, and he grabs them. He then meets Magna, who tells him she's in charge around this place. He tells her he was just going to give them to her.
Later, the heroes are in an iron-barred cage, but they escape, thanks to a magic spell by Dudley. Just then, the laser beast returns. But Dudley uses a magic trick to stop him. Realizing that everything is reversed in this dimension, they recite their respective magic words backward, and are successfully transformed into their superhero counterparts.
Meanwhile, at Magna's house, Sivana asks the young girl where her mother and father are, and she tells him they are still asleep. He then asks her where she got "those lovely dolls," which were actually lizard men. She doesn't tell him until he tells her he won't tell anyone. She then tells him that she had been using her daddy's Dimensional Transporter, which can transport anything to her location. She tells Sivana they could have a race between a Laser beast and the Lizard Men. Sivana tells her that instead she should open every cage and see what happens. While she goes to open the cages, Sivana starts to operate the machine, attempting to transport gold from Fort Knox. The tiny superheroes enter the house unnoticed by the giants, and they head to Magna's parent's room to wake them up. Captain Marvel grabs the father's nose. He then snores and the wind blows him away. Dudley then uses some Sneeze Powder, causing him to sneeze, which wakes both of them up.
Back in Magna's room, Sivana is about to transport riches to his location, when suddenly, the young girl's father, who is much larger than Sivana, enters the room to discipline his daughter. Captain Marvel stops Sivana by destroying the transporter. The father then uses his special rings to shrink Sivana down to his normal size. Her father then returns all of the other "dolls" to their rightful homes, but he decides to let Sivana stay for a while so she can play with him.
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