Bibi & Tina prepare a scavenger hunt on horses for the holiday children of Martinshof. At the same time the valuable silver plates of the Count are stolen from Falkenstein Castle. When Tina accidentally encounters the thieves in the woods, she is locked by them in the Old Mill. Her horse Amadeus escapes. Meanwhile, Bibi is very worried about her friend, who does not return. There she meets Amadeus, who comes alone from the forest. She knows immediately, Tina is in danger!