The Thea sisters continue the search for the seven ancient treasures, using the clues found in Aurora Beatrix Lane's travel diary to find a fabulous emerald which once belonged to Cleopatra--a quest that leads them from Moscow, to the Sahara, and finally Bolivia.
"Geronimo Stilton publicly insults famous Chef Ricardo on his cheese selection in his own restaurant. Geronimo Stilton cuts ahead of an an elderly woman in line. Geronimo Stilton steals ice cream from a little girl. All around New Mouse City, the once upstanding Editor-in-Chief of The Rodent's Gazette is wreaking havoc. Could Geronimo be suffering amnesia? Is he mind controlled? Or has he finally joined the dark side? Only Benjamin, Thea, and Trap...
When a 40 year old letter arrives at Geronimo's house containing only a piece of a treasure map and a mysterious clue, Geronimo and his friends set off to track down the recipient the envelope was intended for all those years ago--even if that means going halfway around the world! It's a globetrotting adventure for the generations!
Geronimo, Thea, and their cousin Trap explore an old castle built by Grant Gentlemouse, the founder of New Mouse City, and when they find one hundred keys and only ninety-nine doors inside, they set off in search of the missing room.