Charlie Piechart and the Case of the Missing Hat

Charlie' friend Margo is missing her hat. It's a princess hat - purple and cone shaped - and she needs it for tonight's play.

With Watson along, Charlie searches for clues all over school. They find a cylinder-shaped hat and a half-sphere hat and lots of purple sparkles, but it's shaping up to be a tough case. . . .

Will Charlie and Watson find Margot's hat before the play begins?