Das Geheimnis der alten Burgruine

While camping near a castle ruin, the Swenson children notice eerie occurrences and are threatened by a giant man who wants to force them to disappear. They meet an orphan girl named Katja, who lives in a cave and warns them about the giant and his friends. When Katja suddenly goes missing, the children venture into the cave and discover smugglers. The smugglers notice them as well and put them in life-threatening danger, from which they can only be rescued with Katja's help. In gratitude, the Swenson family adopts her.