The Mona Mousa Code by Geronimo Stilton #15

Do you like solving mysteries? I do! So when my sister, Thea, heard that there was a secret hidden in Mouse Island's most famouse painting, the Mona Mousa, I knew we had to crack the code! We began to investigate, and soon we were following a trail of clues that led us below the streets of New Mouse City. There we made the most fabumouse discovery....