Nearly two years ago, Meg Kenyon's father left their home in France to fight for the allies in World War II. Recently, Meg heard he had been taken prisoner by the Nazis. All Meg has left of him now are the codes he placed in a jar for her to decipher, an affectionate game the two of them once shared. But even those are running low. But the codes are running low, and soon there'll be nothing left of Papa for Meg to hold on to at all. Suddenly, an impossible...

In 1666, after four months away, friends Christopher Rowe, Tom, and Sally return to London triumphantly but, guided by coded riddles, face a conspiracy that threatens Christopher, as well as the King himself.

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....

As they continue their search for the 39 Clues in China, fourteen-year-old Amy is faced with a terrible dilemma when her eleven-year-old brother Dan suddenly disappears--keep on searching for the next Clue or try to find her brother.

A million dollars, or a clue? Police report a break-in at an elite hotel, and the suspects sound suspiciously like Amy and Dan. There's a car and speedboat chase and an angry mob! When there's a clue on the line, anything can happen.

When a mysterious letter written in code arrives at King's house for his human, Kayla, he follows the trail of the person who left it.

Amy and Dan Cahill are no strangers to impossible tasks. After seven of their relatives were kidnapped, the siblings scoured Europe for the priceless artifacts Vesper One demanded in exchange for the hostages. But then the Cahill kids are given an assignment that pushes them to their breaking point, a journey to a legendary city. Amy and Dan know they can't afford to fail, yet they're running out of options and running out of time.

Fourteen-year-old Amy Cahill and her younger brother Dan thought they could return to their regular lives when they found the 39 clues. But the Vespers, powerful enemies, will stop at nothing to get the clues. And with the Vespers rising, the world is in jeopardy.

The shadow of the man in black has followed fourteen-year-old Amy Cahill and her younger brother Dan on their worldwide search for 39 Clues that lead to a great power. The man has tried to kill them and he is a Madrigal, as were their parents. And now the man is ready to step out of the darkness for their final confrontation.