Below are promo pics for the fourth episode of Merlin’s fourth series, Aithusa.

An old friend of Gaius, but can the mysterious Julius Borden (James Callis) be trusted?

Borden is looking for the final part of the key to the tomb of Ashkanar, where the last dragon egg resides.

As a Dragonlord, Merlin want’s the protect the egg at all costs.

Arthur goes after Borden to stop him from retrieving the egg.

The Knights hit a road block, but Merlin gets them through with a little help.

Aithusa airs Saturday at 8.15pm on BBC1.