Bayard and the knights of the Western Isles are welcomed to Camelot for a feast celebrating a union between the two kingdoms but Nimueh has other ideas. Out to seek revenge on Merlin, Nimueh infiltrates Bayard’s party posing as a waitress. Unaware of her true identity, Merlin befriends Nimueh, who works at trying to gain his trust.
When Nimueh warns Merlin that Bayard plans to poison Arthur, Merlin bursts into the banquet and stops Arthur drinking from a poisonous goblet. But Bayard denies trying to poison Arthur so Uther says that the only way to uncover the truth is for Merlin to drink from the cup himself. As a poisoned Merlin falls into a coma, Bayard and his knights are arrested.
Gaius learns that Merlin has been poisoned by the Morteaus Flower and must be saved from death by an antidote made from the leaf of the same plant. But the rare flower only grows in the caves of Mount Argeaus, deep within the forest of Balor. With Merlin’s health deteriorating, Arthur embarks on a quest to retrieve the flower himself – against Uther’s wishes.
Will Arthur be able to find the flower in time to save his friend – or will Nimueh stop him in his tracks?