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.

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

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.

International bestseller David Baldacci pens the stunning conclusion to Cahills vs. Vespers! It started with a kidnapping. A shadowy organization known only as the Vespers snatched seven members of the Cahill family and demanded a series of bizarre ransoms from around the world. Thirteen-year-old Dan Cahill and his older sister, Amy, began a global treasure hunt, determined to bring back whatever Vesper One needed, so long as it kept the hostages safe.But when they deliver the last ransom, Amy and Dan discover Vesper One's terrifying endgame. The objects he demanded are vital pieces in a Vesper plot that will harm millions of innocent people. Now the two siblings and their friends are in an all-out sprint to stop Vesper One . . . before the whole world goes BOOM.

When the Vespers continue their abductions and cross a line by kidnapping Atticus, an 11-year-old non-Cahill civilian and Dan's only friend, Dan and Amy confront their biggest challenge ever in order to keep Atticus alive.

Amy and Dan have been found unharmed, but perhaps not for long. With the ruthless Irina Spasky is right on their tail, Dan and Amy embark on their most dangerous quest yet, one that brings them face to face with the only force capable of scaring the vicious Lucians: the Madrigals.

When the serum of the 39 Clues goes missing, thirteen-year-old Dan Cahill and his older sister, Amy, do whatever it takes to retrieve it.