Philip and the Thief — John Paulits

After Philip solves a few neighborhood mysteries, he decides to open a detective agency with his best pal Emery. Their classmate Jason starts making fun of their efforts, though, and being a detective suddenly isn't so much fun. But soon Jason is accused of stealing money from the teacher, and Emery encourages Philip to solve the case and get Jason thrown out of their class. Philip sets to work and shocks the class when he reveals the solution to the mystery.