After four days in a row of indoor recess, Miss Mackle's students are bored-until Harry decides to solve the biggest mystery ever in Room 3B! There's a locked closet in the classroom that's been sealed off for years, and he wants to know what's inside. So Harry drafts Doug, Song Lee, and the rest of the class to help him investigate. Their search reveals many surprises-from a hidden trapdoor to...eyeballs! What secret treasures does the closet hold? Is it something more horrible than even Harry can imagine?

Another fun mystery starring Horrible Harry, and this time he's calling the shots! Harry has always loved solving mysteries, and now his friends in Room 3B have learned to love it, too. So Harry challenges them to figure out what he has hidden in his giant, old suitcase. Led by a very determined Mary, the kids take turns solving clues and piecing the mystery together. Their hunt leads them from the classroom to the library, and even to Harry's grandfather's nursing home. Will they be able to solve Harry's mystery? Or will things go horribly wrong for the novice detectives?

When the diamond on Miss Mackle’s engagement ring disappears, the kids in Room 3B are determined to help her find it—especially Harry. The third grade talent show is coming up, and he wants to show off his skills as South School’s greatest detective. Meanwhile, Doug has no idea what to do for his act. He can’t sing like Dexter, or dance like Ida, or solve mysteries like Harry. Now the best friends have to find both Doug’s talent and the teacher’s diamond, or else the talent show will be a horrible disaster for everyone!

Horrible Harry has discovered the biggest mystery ever in Room 3B--a locked closet that's been sealed off for years. Miss Mackle, Song Lee, and the rest of the class join Harry in the detective work, but they soon encounter some surprises. Illustrations.

The kids in room 3B have found out their teacher is engaged! But who’s the lucky groom? Harry goes into detective mode to find out, and Doug is willing to help—until he sees Harry stealing a piece of evidence! Doug can’t believe what Harry has done, but Harry thinks his risky move is worth it. After all, he cracks the case and tells everyone who Miss Mackle is going to marry . . . but does Harry have his facts straight? Or has he made a horrible mistake?

Horrible Harry thinks he?s the world?s second-best detective?second only to Sherlock Holmes, of course. But the rest of the kids in Room 3B aren?t so sure. So he?s determined to prove himself by solving the latest mystery at South School?how to win the new cafeteria contest. He knows the cafeteria lady is using a special mathematical code, but can he crack the code before his classmate Mary tattles on him again? Or will the case go cold right before Harry?s eyes?