Not much time has passed since the thrilling adventure surrounding the stolen treasure of Castle MacGorilla, but our three intrepid investigators—Teddy, Porculina, and Gorilla—are once again called upon to solve a baffling mystery. On this occasion, the action moves from the stark, cold highlands of Scotland to the lush and warmly sunlit Loire Valley in France, but the perils encountered by the trio are no less daunting and the puzzle is, if anything, all the more perplexing.