Melissa & Doug On the Go Secret Decoder - Case of the Slippery Flippers Travel-size Secret Decoder activity and story book with clues to find and a case to solve Includes 18 mystery game activity pages, decoder lens, and magic-reveal pen Special Seek & Find Lens and Spy Pen are easy to use and a valuable addition to any great detectives tool kit Crack the codes and complete the puzzles and games to solve individual mysteries and the whole case Helps teach cognitive development and problem solving, and encourages independent play