Interesting characters and mythology in this episode. I like how they are not afraid to borrow from different sources but they stay fairly accurate to the actual mythology they borrow from.
Sophia and her Father Aulfric are Sidhes pronounced "shee". The are a supernatural immortal race similar to fairies from Irish Folklore. Sophia needs to sacrifice the heart of a Prince to cross through the Gates of Avalon where the Sidhes belong. Her father is willing to sacrifice himself to help her get to this end.
Morgana has a vision of the girl before she arrives and realizes all is not right with this woman. She tells Gaius who realizes that her powers as a "Seer" are growing and advises her to keep it from Uther as he tends to put anyone to death who even thinks about magic.
Gaius realizes what these creatures are and in the end it is up to Merlin, who takes the brunt of the abuse in this episode for Arthur, to save the day.
Uther's reaction to Arthur's announcement of marriage was one of the first times I think Uther seems to have shown common sense in the show. A good show that was very enjoyable with a interesting story and good acting. Thanks for reading...