Doug discovers that though being Harry's best friend in Miss Mackle's second grade class isn't always easy, as Harry likes to do horrible things, it is often a lot of fun.

Follows the school activities of second-graders, Harry and Doug, as they participate in a secret mission to celebrate "Charlotte's Web, " learn how to make green slime, and put on a skit warning about the dangers of smoking.

Horrible Harry and the rest of Miss Mackle's class at South School guarantee fun for the holidays. It all starts when Miss Mackle's reading chair collapses while she's in it!

It's almost summer vacation and the students in room 2B are having trouble concentrating on their butterfly project, until a frightening-looking new teacher comes to supervise the Suspension Room and Harry is sent there as punishment for unruly behavior.

On the last day of second grade, Song Lee's party at the local amusement park forces Harry to face his fear of elevators when he is expected to ride the Drop of Doom.

Horrible Harry sets out to discover who Miss Mackle is going to marry, and he takes some risky moves to be the first one to know.

Inspired by his third-grade class's study of the moon, Harry announces that he is going there.

The students in Miss Mickle's third-grade class enjoy a boat trip on the Connecticut River after a class discussion of ancestors reveals that Sidney and Ida both have connections to the sea.

Harry persuades his classmates to sneak through the playground fence during lunchtime recess to view some unusual mushrooms.

Harry and his detective classmates try to find clues relating to a mysterious locked closet in Room 3B.