Merlin’s adventures continue on Saturday with the fourth episode of 13, Aithusa.

The mysterious Julius Borden arrives in Camelot with news of a magical secret that threatens to change the landscape of the kingdom for ever. He has located the final part of the key to the tomb of Ashkanar – an ancient mausoleum which holds a very special treasure: the last remaining dragon’s egg. Merlin is understandably drawn in by Borden’s news and promises to help him. But just who is this enigmatic stranger and, more importantly, what does he really want with the egg?

Trailer: