It's Christmas time in Mousehole and Georgia and Olivia are on a new quest into the past. But what extraordinary events will unfold in their own world as a result? When the girls help Joey and his father to discover the truth about their history, they learn about the 'eternal secret' of the crystal skulls. Can Vicky and Bex help them to uncover the eternal secret? And are they alone in seeking to unravel the mysteries of the skulls?