Horrible Harry and friends start off third grade with a new room and a field trip to an old copper mine to study rocks.

Herbie's experiences in the third grade include finding bones in the boy's bathroom, wandering away from his class on their field trip, and being promoted to a higher reading group.

Disaster strikes when Annabelle trusts Herbie Jones and Raymond with the job of picking up the class's gift to their teacher.

Herbie's friend Ray and some classmates in his fourth-grade reading group help him adjust when he moves into a new bedroom in the attic.

Morty Hill worries that his best friend Molly Zander will get in trouble at school when a new classmate tells that Molly is the one who knocked off the principal's toupee.