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.

Unable to return to their normal lives despite the end of the Clue hunt, new Madrigal leaders Amy and Dan anxiously prepare for a retaliatory strike by the Vespers, who kidnap a number of Cahill family members and demand that Amy and Dan steal a famous painting.

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.

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.

When biochemist Emma Caldridge applies for kidnapping insurance, it's denied. Sebastian Ryan, the risk analyst for the insurance company, takes one look at her history of winding up in the wrong place at the wrong time and deems her a "statistical nightmare." But for Ryan the nightmare is just beginning, and he'll need Caldridge's assistance if he's going to survive.

A guide to the characters and situations in "The 39 Clues" outlines the Cahills' secrets, including hidden facts, strategies, agents, lost founders, secret bases, and scandals, as well as information about all branches of the family.