Amy and Dan continue their search for the clues and cross oceans amid ruthless enemies and dangerous truths while following the trail of a famous aviator.

Thirteen-year-old Dan Cahill and his older sister, Amy, are the latest guardians of the Clues -- thirty-nine ingredients in a serum that transforms whomever takes it into the most powerful person on earth. They think they've done everything right, but a tiny mistake leads to catastrophe. The serum is missing and Dan and Amy have to get it back and stop who stole it ... before it's game over.

When Alfie McQuinn, the notorious jewel thief, is killed on a job, his last words to his son, March, are to "find jewels" and this instruction leads the boy to Jules, the twin sister he never knew he had--and the perfect partner to carry on the family business.