Ehh. This is just your basic creature feature, really.
From the SyFy Channel's official site:
"A mysterious illness draws Merlin to a distant village. But it soon becomes clear that there is more at stake than just his patients' well-being as something sinister turns the air sour. Realizing he is out of his depth, he resolves to return to Camelot and fetch Gaius.
On the way, however, Merlin and the knights encounter a girl being accosted by bandits. They rescue her, but all is not as it seems, as time spent with the girl begins to turn the knights hostile and make returning her home a fixation in their minds.
Fearing for Merlin and the lost knights, Arthur, Gaius and Agravaine visit the original village. There, Gaius concludes that the cause of the illness was Lamia, who is not a girl, as she appears, but actually a magical creature in disguise. Arthur and Agravaine go in search of their lost party and, despite the latter's efforts to foil the effort, eventually track them to an abandoned castle with some help from Gwen.
Meanwhile, at the castle, the Lamia is picking off the knights one by one. Merlin remains immune, however; a happenstance of which Gwen takes note. Merlin eventually engages in a magical duel with the creature, which has now transformed into a monstrous creature, but just as Merlin is about to unleash his strongest attack, Arthur arrives, and slays the beast with a spear. The party then returns to Camelot, where Gaius is able to heal those afflicted with the Lamia's infectious curse."
After last week's near-feature (whose final scene almost made me cry, by the way), this one is a real letdown. Other than Gaius' interesting choice to trust Merlin with a medical errand, nothing is really revealed about the characters, and none of the ongoing plots are advanced. Indeed, it seems a poor choice on the writers' part to fritter away all the momentum built by The Secret Sharer on a monster story.
And yes, that's what Lamia is: a formulaic monster story. A mysterious Something is attacking a remote village. A party rides out from Camelot to investigate. Said party gets ensnared by the monster, necessitating a heroic rescue. Check, check, check. Granted, I was pretty tired Friday night, but I was definitely going cross-eyed with this one about twenty minutes in.
Oh well -- maybe next week's Zombie Lancelot episode will be better.
As I note above, this script isn't very interesting.
And the acting doesn't stand out either.