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!
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.
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 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.
When Horrible Harry's pet cat, Googer, sneaks a ride and gets into the school building, third-graders Harry and Doug have to catch him before anyone else does, which means going into some forbidden places.
"The kids in Room 3B are asked to draw posters of things that they love, and one of them will get to share his or her poster on TV"-- Provided by publisher.
Harry's interest in solving mysteries has caught the attention of his classmates in 3B, so he challenges them to discover what he has hidden in a giant, old suitcase.