From totalscifionline:
When Gwen is imprisoned for sorcery, Merlin comes up with a lunatic plan to free her...
And so the strands continue to entwine, bringing the BBC version of Camelot further in line with standard Arthurian myth. The set-up of Gwen being a serving girl, rather than royalty in her own right, has always been one of the biggest areas of difference between the two. While inevitably there's no "happy ending" in this episode, with Arthur and Gwen's love blessed by Uther, the seeds are sown for a future Camelot with them ruling together.
Morgana's machinations are beginning to become obvious to more people, although there's a bit of a continuity error here caused by the move forward in the running order of ‘The Eye of the Phoenix’, which saw Gwen already suspicious of her. It's a minor glitch but one that should have been picked up.
The real treat in this week’s episode, though, is Colin Morgan playing the aged Merlin, in the traditional garb with long flowing hair and beard. The writers make a plot point of the lack of change to Morgan's eyes, but otherwise the make-up is very well-achieved, and the scenes with the old sorcerer talking to Arthur and Uther are a treat.
A strong ensemble episode that would have scored higher but for the error. Paul Simpson
VERDICT: 8/10
http://totalscifionline.com/reviews/5764-merlin-queen-of-hearts-series-3-episode-10