In the sixth volume of the 39 Clues series, Amy and Dan fly to Australia. Attempting to trace their late parents' journey eight years earlier, they link Amelia Earhart's last flight to their own family quest. While Amy deals with increasingly intense memory flashbacks related to her parents' deaths, she and Dan must cope with ravenous sharks, poisonous spiders, and their rivals' fiendish schemes. The spy-versus-spy mentality will keep readers guessing as they try to separate deception from reality. Although the complex backstory looms large, the series' fans will devour the breathless action scenes in this fast-paced adventure.

Good-hearted siblings Amy and Dan continue their globetrotting quest for the clues that will unlock the power of their historically uber-powerful family. The series still pushes credulity past the tipping point, but these installments introduce new developments (heretofore cartoonish competitors reveal hints of humanity; the sibs' stalwart nanny becomes suspicious; clues to their parents' death surface) that rejuvenate the foundering plots.