Doug discovers that though being Harry's best friend in Miss Mackle's second grade class isn't always easy, as Harry likes to dohorrible 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.

The students in Miss Mackle's third-grade class enjoy a day of Halloween surprises, including Harry's unusual costume.

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.

Miss Mackle's third graders share December holiday traditions--Christmas, Hanukkah, Kwanzaa, Three Kings Day, and Korean New Year--with each other and with Harry's great grandfather, who has just moved to a nursing home.

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

When Sid, his annoying third-grade classmate, ruins Song Lee's origami praying mantis, Horrible Harry plots triple revenge on the troublemaker.