Something very strange is happening around Lewisville. As usual, young teenagers and best friends Griff, Frank, and Chase find themselves right in the middle of the unfolding mystery! Clues begin to emerge, starting with the appearance of a black speedboat lurking on the New Haven River. Next comes an urgent weekend meeting called by the head of the Lewisville Bank. The arrival of two Secret Service agents and the unexplained disappearance of a peculiar, elderly landowner place the Bon Air Boys on high alert to get to the bottom of the seventh mystery in this wholesome adventure series. Grab your walkie-talkie and hop on your bicycle as you join your favorite young sleuths in this fast-paced, suspenseful, and satisfying story.