The stone of fire got stolen by the new mouse city's worst enemy, a cat. So Geronimo Stilton had to find the cat and get the stone of fire back to new mouse city's museum. Geronimo had to travel to the island where the cats were and he had to somehow try to steal it. But one of the cats army trapped Geronimo in a box and took him to the king (of the cats) to have him for lunch. But one of Geronimo's friends came to the rescue and tricked the cats and he also stole the stone of fire.
The book was alright it wasn't the best but I enjoyed reading it.
I would rate it 7-10