Margaret Peterson Haddix

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,...

Follows fifth grader Max as he searches for his best friend who disappeared, leaving behind a strange note.

A twelve-year-old girl raised in a foster village is returned to her biological parents, and discovers home is not what she expected it to be.

When thirteen-year-olds Jonah and Chip, who are both adopted, learn they were discovered on a plane that appeared out of nowhere, full of babies with no adults on board, they realize that they have uncovered a mystery involving time travel and two opposing forces, each trying to repair the fabric of time.

Time-travelers Jonah and Katherine are summoned to help another missing child from history, this time Virginia Dare from the Roanoke Colony, but their journey is sabotaged and goes dangerously awry, leaving them in the wrong time period. Includes author's note about the history of Roanoke Colony and Virginia Dare.

Thirteen-year-old Nina is imprisoned by the Population Police, who give her the option of helping them identify illegal "third-born" children, or facing death.

In a society that allows families to have only two children, a group of third-borns tries to save themselves and others like them.

After secretly receiving injections at the age of 100 that are meant to reverse the aging process, Melly and Anny Beth grow younger until, as teenagers, they try to find a guardian to take care of them as they return to infancy.

Jonah, Katherine, Chip, and Alex suddenly find themselves in 1483 at the Tower of London, where they discover that Chip and Alex are Prince Edward V and Richard of Shrewsbury, imprisoned by their uncle, King Richard III, but trying to repair history without knowing what is supposed to happen proves challenging. Author's note includes historical facts about the princes and king.

Jonah was able to save all of time from collapsing but in doing so gained a twin brother, Jordan, who must learn what has happened and do his own part to save time--and his parents.