Episode Name: Lamia
Air date: 11/19/2011
Summary: Merlin is drawn to a distant village when a mysterious illness strikes. However, it soon becomes clear that something sinister turns the air sour and that there is much more at stake than just his own well-being. Far from home and having to fare by himself, Merlin becomes entangled in a deadly game of cat and mouse where he can trust no one. Confused about who is the hunter and who is the hunted, will the young warlock be able to survive long enough to find out the truth?      

Watch or download Merlin – Season 4 Episode 8 – Lamia at below links.