When seven members of their family were kidnapped, thirteen-year-old Dan Cahill and his older sister, Amy, got ready for the fight of their lives. But their enemy, a terrifying group known as the Vespers, remained frustratingly elusive. They stay in the shadows, picking off Cahills one by one.And now the Vespers have landed their most serious blow yet - a blow that strikes at the very heart of the Cahill family. Because Amy and Dan discover that there's a Vesper mole in their innermost circle. Amy and Dan need to smoke out the traitor before the next hostage dies. They have just days to discover who has their back . . . and who wants to sink a knife into it.

Are you ready to save the world? The bestselling series returns with an adventure spanning 6 explosive books, 2 secret-filled card packs, and a website that places readers right in the action. Thirteen-year-old Dan Cahill and his older sister, Amy, thought they belonged to the world's most powerful family. They thought the hunt for 39 Clues leading to the source of that power was over. They even thought they'd won. But Amy and Dan were wrong.One by one, distress calls start coming in from around the globe. Cahills are being kidnapped by a shadowy group known only as the Vespers. Now Amy and Dan have only days to fulfill a bizarre ransom request or their captured friends will start dying. Amy and Dan don't know what the Vespers want or how to stop them. Only one thing is clear. The Vespers are playing to win, and if they get their hands on the Clues . . . the world will be their next hostage.

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.

After delivering the last ransom, Amy and Dan discover that Vesper One has a terrifying plot and they race against time to stop him from harming millions of innocent people.

C.1, GENERAL FUNDS, SAM'S, 3/23/2010, $12.99.

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.

When you're with Geronimo Stilton, it's always a fabumouse adventure!