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
The Vespers have Atticus Rosenbloom and will kill him if Dan and Amy do not comply with their demands. Vesper One commands Amy and Dan to find a stale orb, an anagram for astrolabe. They fly to Samarkand, Uzbekistan, to find the astrolabe. Atticus escapes, and Dan suspects that his father murdered William McIntyre and is Vesper One. Ian goes to New York, suspecting Isabel to be Vesper One, and Isabel manipulates him into staying by saying that the other Cahills are not his friends. The hostages are rumored to be in Argentina because of a lizard Nellie holds in a photo. Dan has gathered seventeen ingredients of the thirty-nine for his own master serum. He has also been receiving texts from a Vesper claiming to be his father, so he texts back a question to confirm this and is shocked that the answer is correct.