Pete and Penny live above Pizzarelli's, the family pizza parlor, in the small town of Rellaville. They're excited when their parents go out of town, leaving them in charge along with their quirky uncle. But everything goes downhill fast when the family's top-secret pizza sauce recipe is lost! Readers figure out puzzles alongside the main characters and those clues lead them to solve the mystery!

Pete and Penny live above Pizzarelli's, the family pizza parlor, in the town of Redville. A bookstore opens next door and strange things start happening there - bookshelves collapse, the fire alarm goes off, books disappear! Is someone trying to sabotage the new bookstore? When a secret message appears in the wall between the two stores, Pete and Penny start to puzzle it out. They need your help!