The 39 Clues is unstoppable! The bestselling series returns with an adventure spanning four explosive books and a website that places readers right in the action.

The Cahill family has a secret. For five hundred years, they have guarded the 39 Clues — thirty-nine ingredients in a serum that transforms whomever takes it into the most powerful person on earth. If the serum got into the wrong hands, the disaster would rock the world. So certain...

Nora and Ben's younger sister Birdy loves to keep secrets. She surprises her family more than once: She hides a kitten in her room. She writes a beautiful poem. One day Birdy watches her mother spit into a tube, ready to send it off to find out more about herself and where her family came from. Birdy spits into a tube, too, when no one sees her. But when the test results come back, they are a surprise. Birdy is seemingly not related to Nora and Ben's...

For Arlo Finch and the Rangers of Pine Mountain Company, summer camp is more than canoeing and hiking. It's also a chance to search for ancient forest spirits and discover mysterious messages encoded in tree bark. But when Arlo and his best friends Indra and Wu stumble upon clues about the long-lost Yellow Patrol, Arlo uncovers a stunning history that leads right back to his very own family.

When Amy and Dan Cahill trace the footsteps of a formidable military leader from the Cahill bloodline, they uncover a devastating secret about the family that changes everything.

1919. Mama is ill. Father has taken a job abroad. Nanny Jane is too busy to pay any attention to Henrietta and the things she sees--or thinks she sees--in the shadows of their new home, Hope House. All alone, with only stories for company, Henry discovers that Hope House is full of strange secrets: a forgotten attic, ghostly figures, mysterious firelight that flickers in the trees beyond the garden. One night she ventures into the darkness of Nightingale...