A Clue found in Book 3 sends Amy and Dan jetting off to find out just what's behind the fierce rivalry between the Tomas and Ekaterina branches of the Cahill family. Was a Clue stolen from the Tomas branch? Where is it now? And most important, can Amy and Dan get their hands on it before their rivals do?

"Forty years ago, Steven Smith found a copy of a famous children's book by disgraced author Edith Twyford, its margins full of strange markings and annotations. Severely dyslexic and wanting to know more, he took it to his remedial English teacher Miss Iles, not realising the chain of events that he was setting in motion. Miss Iles became convinced that the book was the key to solving a puzzle, and that a message in secret code ran through all Twyford's...

"The week before New Year's Eve and genealogist Lucy Lancaster is mixing work and play quite nicely at the boutique Sutton Hotel in Austin, Texas. After two months of research she's finalizing her presentation for hotel heiress Pippa Sutton. When a strange man comes staggering toward her and presses a classic Montblanc pen into her hand, he whispers, 'keep them safe,' and collapses at her feet, dead. Lucy's grandpa is a collector, but has an odd reaction...

Dr. One-Zero won't stop until the whole town--no, the whole world--embraces the "true happiness" found in his poisonous potion, Green Pop. And now that he has the Turtle of Light, he's virtually unstoppable. There's one weapon that can defeat him: another Turtle of Light. Unfortunately, they can only be found in another dimension! To open a portal to this new world, Hopper, Eni, and Josh's coding skills will be put to the test.