Episode Name: The Darkest Hour, Part 2
Air date: 10/8/2011
Summary: The kingdom is on the brink of collapse, with Morgana poised to strike. As Lancelot races back to Camelot with the dying Merlin, Arthur must continue on his mission to vanquish the Dorocha without them. Though the Knights know their journey to the Isle of the Blessed is fraught with danger, none could anticipate the sacrifice Arthur intends to make there. Friendship and loyalty are tested to the limit, but in the end, it is the power of love that changes all their lives forever…      

Watch or download Merlin – Season 4 Episode 2 – The Darkest Hour, Part 2 at below links.