Traveling to Brazil to locate a rare crystal treasure being guarded by a native tribe in the Amazon jungle, Geronimo Stilton and his friends navigate a treacherous route filled with crocodiles, giant rats and, piranhas.

Holey cheese -- my sister, Thea, was in danger! She had traveled to Easter Island in search of a secret treasure, and now she needed my help. There was no time to lose! My friends and I hopped on a plane to begin our search, aided by a map and a mysterious riddle. What an exciting adventure!

When he begins receiving packages containing useless things he did not order, Geronimo Stilton discovers that someone on the Internet has stolen his identity, a dilemma that compels him to enlist the help of computer expert Professor Margo Bitmouse, who helps Geronimo track down the hacker.

"When you're with me, Geronimo Stilton, it's always a fabu-mouse adventure! Sally Ratmousen broke some shocking news: The Rodent's Gazette was out of money and in danger of closing. Then Grandfather William broke even worse news to me: I needed to sell my comfy, cozy house in order to save our paper! How terrible! But could I sell it -- and find a new home -- in time to help?"--Back cover.