At 13 Conspiracy Street, everything exudes mystery: the long corridors, the creaking stairs, the dark office illuminated by the light of a single candle... And right here, sitting in his Armchair, the great detective Sherlocko dedicates some time every now and then to play a game of chess! But if his opponent is his assistant, Geronimo Stilton, he has already won... because no one is as ingenious as Sherlocko! The adventures of Sherlocko Cases that are impossible to solve? Don't worry! With the great Sherlocko and his assistant... that is, me, you're in good hands. Follow us in our investigations, from one clue to the next until the mystery is solved. We will experience an adventure... Sherlockian. On the honor of Stilton, Geronimo Stilton 2. THE CAT'S MARK A... Catmouse is roaming around Ponticton, scratching the city's most precious works of art with its claws. But are there Catmice? The great Sherlocko doesn't believe it and, along with his assistant, begins the investigations. They must save Ponticton's works of art. An exciting case, with an... unexpected ending!