Just after twelve-year-old Emily and her family move to San Francisco, she teams up with new friend James to follow clues in an odd book they find, hoping to figure out its secrets before the men who attacked Emily's hero, publisher Garrison Griswold, solve the mystery or come after the friends.

Mr. Quisling is definitely up to something mysterious, and Emily and James are on high alert. First, there's the coded note he drops at a book event. Then Emily and James uncover a trail of encrypted messages in books by Mark Twain hidden through Book Scavenger. What is most suspicious is that each hidden book triggers an arson.