A boy is washed up on the rocks in St Thomas Bay, Malta. He is injured and unable to speak. Who is he? What terrible secret is he hiding? All Josephine knows is that he needs her help. She cannot tell her parents in case the boy is one of the refugees her father says should be sent back to their own country.

Jo enlists the help of her friend Andreas. Together they find a hiding place for the rock boy, but it becomes harder and harder to keep their secret. Finally, the only safe place left is The Hypogeum, an ancient underground temple that holds the bones of thousands of people killed in ritual sacrifice...