Jana and Max observe a shadowy figure sneaking into a house. However, no burglary has been reported to the police. Jana and Max decide to investigate on their own and move into the treehouse for this purpose. The dark figure is also seen lurking around the following night. Again, nothing was stolen. But two days later, just when the treehouse spies are unable to observe anything for the first time, a lady reports that five thousand euros have been stolen from her - now the case really picks up speed...