The explosive finale to the #1 bestselling series! Fourteen-year-old Amy Cahill and her younger brother, Dan, have had enough. Not only do they have to find the 39 Clues first, they're expected to reunite their backstabbing family - the same people who killed their parents. But Amy and Dan haven't survived explosions and assassination attempts for nothing. They have a plan to finish the Clue hunt on their own terms. Too bad there's a final, fatal secret the Madrigals haven't told them. A secret that could cost Amy and Dan - and the world - everything.

Throughout the hunt for the 39 Clues, Amy and Dan Cahill have uncovered history's greatest mysteries and their family's deadliest secrets. But are they ready to face the truth about the Cahills and the key to their unmatched power? After a whirlwind race that's taken them across five continents, Amy and Dan face the most difficult challenge yet - a task no Cahill dared to imagine. When faced with a choice that could change the future of the world, can two kids succeed where 500 years' worth of famous ancestors failed?