A suspicious bill, a coded plea, and the Graham Quartet are ready for action!

Out along the lonely stretches of Old Elm Road, the Graham Quartet feels a mystery brewing. When a string of strange happenings continues to point in the same direction, Elsa, Matt, Selena, and Tim are determined to get to the bottom of things. But are all of these oddities really connected? Or is the Quartet so eager for another mystery that they're making up trouble out of nothing? When their old friend Guy Fox steps in to investigate, things take a startling turn. Will the four siblings have the right clues to piece everything together before the crooks get away?