The 39 Clues - Book 10: Into the Gauntlet

Into the Gauntlet is the tenth and final book in The 39 Clues novel series. It was written by Margaret Peterson Haddix  and released on August 31, 2010. In the beginning of the book, Amy and Dan think about if they ever should have joined the clue hunt, and every misfortune they've had. Their lead is a poem found in their hotel room. However, it is then stolen by Isabel Kabra.