Mr. Merlin's Third Graders are known as the Third Grade Detectives -- with some hints from secret code clues and help from Mr. Merlin's friend, the police scientist Dr. Smiley, they help solve cases. This two-in-one flip book contains the full text and illustrations for the first two Third Grade Detectives books. In their first case, The Clue of the Left-Handed Envelope, the Detectives find out who has been sending Amber Lee anonymous letters. And in their next case, a dirty handkerchief provides a clue to who's been trespassing in Todd's tree house.