The 39 Clues - The Emperor's Code

One belif has sustained fourteen-year-old Aamy Chill and her youger brother, Dan, on their hunt for the 39 Clues: they are the good guys.
But then a shocking discovery about their parents shatter everything Amy and Dan think they know, dividing the two siblings for the first time ever.
When Dan disappears in a country of more than a billion people, Amy has to make a terrible choice - find the next Clue . . . or find her younger brother.