"Master detective Kalle Blomquist and his friends are ambushed in an old ruin by members of an enemy gang. Kalle and Eva-Lotta are captured but manage to free themselves. When Eva-Lotta returns to the ruin a day later, she discovers the corpse of a old man. She tells the police that she could recognize the perpetrator, who had fled from the unwelcome witness.Her name is announced by a newspaper and Eva-Lotta is in grave danger."