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. Now the serum is missing. Dan Cahill and his older sister Amy have to get the serum back and stop who stole it...before it's game over. For everyone.

FINAL HOURS Tick tock. Fifteen-year-old Amy Cahill has only a few days to live. There's a poison coursing through her, and her only chance is to collect ingredients for an antidote. Too bad the antidote's ingredients are scattered around the world. And too bad that survival is by far Amy's smallest problem.The antidote she needs is also the only thing capable of stopping a deadly enemy. J. Rutherford Pierce is on the brink of becoming the most powerful man in the world, and if he does, no one will be safe. Amy and her younger brother, Dan, will do everything it takes to bring Pierce down. Even if Amy must pay the ultimate price.

Guardians of the 39 Clues, Dan Cahill and his sister Amy discover that the serum is missing and must race against time to get it back before catastrophe strikes

Life or Death The clock has run out for thirteen-year-old Dan Cahill. As head of the most powerful family the world has ever known, he and his older sister, Amy, have been in the crosshairs for too long. Dan and Amy have always managed to stay a step ahead of their enemies, but it was only a matter of time until luck failed them.Now Dan is hopelessly trapped and nothing can save him. Nothing except unleashing an evil into the world even worse than the enemies closing in. As Dan hovers between life and death, Amy has a terrifying decision to make. Just how far is she willing to go to save her little brother?

The heart-stopping 39 CLUES series returns with an even deadlier challenge, as a new enemy is revealed to be searching for The 39 Clues too... Amy and Dan's race to save the hostages reaches its thrilling conclusion. Who will be victorious? The Cahills or the Vespers?