Tiril and Olivier are a pair of young detectives. Together with their faithful dog friend Ocho, they will solve every puzzle. One day, friends find mysterious holes in the ground. Something that seems like a threat to cyclists is actually the beginning of a more complicated matter. The mysterious Man in Black who is looking for treasure is prowling the area. Young detectives are starting an investigation that goes back to the history of the town and its inhabitants.
What is a masked villain looking for? Will finding a map from the past allow a breakthrough in the case? Will the truth see the light of day? The highest-quality family detective story and adaptation of the popular book from the series Operation.