Freckles shows up at the home of Billy Batson and the rest of the Marve Family, with a strange book she bought from an old pedller. However, that peddler was the villain Ibac, and once everyone's asleep reptilian Hiss-Men emerge from the book and capture the Marvels, taking them to a strange tube that leads to prehistoric times.
There, the Marvels are changed into Hiss-Men with a speech impediment that keeps them from being able to say their magic words. Ibac reveals a plan to help the Hiss-Men take over the primitive human race. Eventually Billy manages to escape and turn back to normal, then helps Mary and Freddy turn back and thwart Ibac's plan. He's left in prehistoric times fleeing a dinosaur when the Marvels return to the present, then take the time travel tube and hurl it into the sun.