The Medusa Plot is the first book in the Cahills vs. Vespers series. The book was written by Gordan Korman and released on August 30, 2011. The story picks up two years after the original series The 39 Clues and is about the Cahills' attempt to save members of their family that have been kidnapped by following the instructions given by Vesper One. The code that appears between pages 39 and 61 reads "The mother was murdered."