When George and Harold hypnotize their principal into thinking that he is the superhero Captain Underpants, he leads them to the lair of the nefarious Dr. Diaper, where they must defeat his evil robot henchmen.
Isabel is enchanted with an old photograph of her great- grandmother, taken when she was about Isabel's age. An imaginary dialogue develops between the two and from the mixture of the two generations with their differing points of view, clothes and lifestyles, a new personage emerges.
After learning that he is the son of a mortal woman and Poseidon, god of the sea, twelve-year-old Percy is sent to a summer camp for demigods like himself, and joins his new friends on a quest to prevent a war between the gods.