The Medusa Plot is the first book in the Cahills vs. Vespers series. It takes place two years after the Casper Wyoming Incident in Vespers Rising. It was written by an author Gordon Korman, and was released on August 30, 2011. The logo on the cover of The Medusa Plot is red as opposed to the blue logo on the other 39 Clues books. Also, the six Cards' design and inside design are different from the other books'.