One False Note
One False Note is the second book in "The 39 Clues" series. It is written by Gordan Korman, and was published by Scholastic on December 2, 2008. Following the events of "The Maze of Bones", the protagonists Amy and Dan Cahill learn about Mozart and travel to Vienna, Austria to search for the second clue in the 39 Clues competition. "One False Note" entered the Children's Books New York Times Best Seller list at number one on December 21, 2008 and stayed on the list for children's chapter books for 12 weeks.
The 39 Clues
Two years after the Clue hunt, all who succeeded in finding Gideon's serum recipe have united. The feud between the Cahills has ended, and the family unites to battle a new enemy: the Vespers, a secret organization led by Vesper One who have been the Cahills' enemies since the time of their ancestor Gideon. Members of the Cahill family are kidnapped and will be returned only if Dan and Amy follow Vesper One's instructions.