Nowhere to run - Jude Watson

The Cahill family has a secret. For five hundred years, they have
guarded the 39 Clues - thirty-nine ingredients in a serum that transforms
whomever takes it into the most powerful person on earth.
If the serum got into the wrong hands, the disaster would rock
the world. So certain Cahills have always made it their mission
to keep the serum safe, buried, locked away. Until now.
Thirteen-year-old Dan Cahill and his older sister, Amy, are the latest
guardians of the Clues. They think they've done everything
right, but a tiny mistake leads to catastrophe. The serum is missing
and Dan and Amy have to get it back and stop who stole it . .
. before it's game over. For everyone.