In the second book, the adventures in prehistory continue. Katherine, Trevor and Chryseis embark on an amazing ship and sail to remnants of the sunken continent of Atland. When a stolen speaking stone is found in their luggage everybody suspects the three friends. Will the time travellers be punished for the theft? Suddenly, everybody is after the mysterious stone from the fabled land of Lyonesse and some of the strange sea creatures are not as amusing as they seem.They escape - only just - a trap set by sorcerers in Prydhain and receive help from an unexpected source. Then the speaking stone has something to say...