Gwen faces an impossible dilemma when she is forced to choose between saving the life of Elyan, her estranged brother and only sibling or Arthur's, Camelot's prince and the love of her life. When one of them is certain to find death at the hands of Cenred, who will Gwen choose?

Once again, loyalty, love and friendships are tested to the limit as Arthur, Merlin and Gwen are forced to put their minds together to try and find a way out of the cruel quandary. Morgana and Morgause, in turn, will do their best ruin their plans.

Will good conquer evil or will Gwen end up losing someone she loves again?

Arthur and Merlin embark on a dangerous mission to capture the Cup of Life, a powerful magical artifact that carries the gift of immortality. However, before they are able to retrieve the Cup they fall prey to Jarl, an unscrupulous slave trader. They manage to escape when a trusted friend comes to their rescue but with Jarl's help, the Cup of Life ends up in Morgause's hands. Now that the dreadful sisters count on an immortal army at their disposal, will Morgause and Morgana overthrow Uther once and for all?

Will Arthur be able to save Camelot from the evil Morgana? Morgana, newly crowned as Queen of Camelot, begins a reign of terrible evil over the innocent citizens of the kingdom. Counting on Morgause and her immortal army at her command all hope seems lost for Uther, who is forced to witness how his kingdom crumble under the unimaginable cruelty of his own daughter. Meanwhile, on the outskirts of Camelot, Arthur recovers his strength and plans a counter attack with the help of a few loyals at his side: Gwaine, Lancelot, Elyan and Percival. However, Merlin is aware that not even a skilful warrior like Arthur can defeat an immortal foe without magic. Will he be able to reclaim the great sword Excalibur from the Lake of Avalon in time to save the lives of those he cares the most about?