The Poisoned Chalice

"The Mark of Nimueh" is the fourth episode of the first series of Merlin, which was broadcast on BBC One on 11 October 2008.

Plot
With her sights set firmly on Merlin, Nimueh tricks him into drinking from a poisoned chalice, and he falls desperately ill. Arthur ventures deep into the forests of Balor to find an antidote, but little does he know he's walking into a trap.