Cotton Malone battles a group of families whose influence dates back to the American Revolution and who seek to crack a code devised by Thomas Jefferson himself in their quest for power.

Dan and Amy Cahill travel to Egypt to hunt for 39 clues, when they get a surprise communication from their dead grandmother, Grace.

Amy and Dan, wanted by the Indonesian police and stranded on an island with a tropical storm on the way, are about to discover a terrible truth about their branch of the Cahill family.

An escalating race to find the 39 Clues finds Amy and Dan pursuing a Clue guarded by thousands of the world's best-trained soldiers, an effort that separates them in explosively dangerous ways.

Operation Trinity chronicles the first Vesper attack on Jan van Eyck's altarpiece at Ghent in the 1600s, then jumps to WW II and young Grace Cahill's desperate bid to save the masterwork from the Nazis.

When Amy and Dan learn the truth about the Madrigals and Grace Cahill's alternate will, these discoveries lead to the revelation of a secret about their family and a showdown with the man in black who has been following them.

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 the difficult challenge yet -- a task no Cahill dared to imagine. When faced with a choice that could change the future of the world,...

Scholar Jules Addison and scavenger Amelia Radcliffe join forces to unravel secrets of a long-extinct civilization, only to discover something that could spell the end of the human race.

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.