Oracles of Delphi Keep

Ian Wigby is about to find out that he is a very special boy.
Along the southern coast of England, atop the White Cliffs of Dover, stands a castle. And at that castle’s old keep is an orphanage. Delphi Keep has seen many youngsters come and go through its gates, and Ian Wigby and his sister, Theodosia, are happy to call it home. Life has always been simple at the Keep, and the orphanage safe, until one day, Ian and Theo find a silver treasure box. And within the box, a prophesy. Three thousand years ago a great Greek oracle wrote of a quest. A quest on which the fate of the world depends. A quest that names two children—Ian and Theodosia. Suddenly Delphi Keep is no longer safe. And Ian and Theo, along with a very special group of friends, realize they must unravel the meaning behind the scroll of Dover cavern before darkness falls on the world. And before an unfathomable evil catches up with them.
From the Hardcover edition.