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,...

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.

In a future where the law limits a family to only two children, third-born Luke has been in hiding for the entire twelve years of his life, until he enters boarding school under an assumed name and is forced to face his fears.

In a society that allows families to have only two children, third child Matthias joins the Population Police to infiltrate their system.

When thirteen-year-old Luke Garner unwittingly sets off a rebellion which sweeps the country and ousts the Population Police from power, he quickly realizes that the new regime is corrupt and he may hold the only key to true freedom.

When Jonah and Katherine travel to early 1900s Switzerland and Serbia to return Albert Einstein's daughter, Lieserl, to history, her mother Mileva grasps entirely too much about time travel and has no intention of letting her daughter go.

Thirteen-year-old Bethany's parents have always been overprotective, but when they suddenly drop out of sight with no explanation, leaving her with an aunt she never knew existed, Bethany uncovers shocking secrets that make her question everything she thought she knew about herself and her family.

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.

While ten-year-old Anya faces the difficulties of losing her hair to alopecia, her classmate Keely learns how to stand up for what she knows is right.

After returning the missing children from history to their original time periods, thirteen-year-old Jonah must save time itself when aviator Charles Lindbergh mysteriously appears and kidnaps Jonah's sister.