Lucky Starr and the Big Sun of Mercury

Once filled with the sounds of human life, now barren caves. It was Lucky Starr's job to find out who or what had disrupted the needed flow of minerals to Earth.

• Was it the Sirians, preparing for an all-out attack on Earth?
• Was it Rock Creatures, delighting in helpless victims?
• Were the stories stammered by terrorized miners, stories of phantoms haunting the dark shafts, true?

The Council of Science had sent Lucky to find out the truth...