Les Cinq et la fortune des Saint-Maur

The Five are sent to the Iris Chalet where Jeanne, the Lagarde housekeeper, lives. They go to the ruins of an old manor nearby, the Saint-Maur manor. They are surprised by a terrible storm. When they return to the Iris, they discover a casket at the foot of a charred oak tree struck by lightning. Who would have guessed that the famous Saint-Maur treasure was hidden here? But this one has surprises in store for the Five!