The mystery of Mr. Nice from the tattered casebook of Chet Gecko private eye

Most folks know him as the best lizard detective at Emerson Hicky Elementary, but it's not all knuckles and know-how with Chet Gecko. He's also got his artistic side.
If it wasn't for his art, he might never have been sent to Principal Zero's office, where he stumbled onto the mystery of Mr. Nice. Because whatever you can say about Principal Zero, one thing is certain: He is not nice. Until now.
Chet knows something is wrong with this picture, and he's just the gecko to solve this mystery. After all, who do you think put theartin smart aleck?