Desperate for revenge against Merlin, Morgana joins forces with the enigmatic wizard Alator conspire in the abduction and framing of Gaius. Agravaine's machinations convince Arthur that the old apothecary is a traitor, and when he's kidnapped by Alator, the king's suspicions are inflamed. It's up to Merlin, of course, to set things right.
Gwaine rescues Gaius, but not before Alator is able to extract the information that Merlin and Emrys are one and the same. But just when it seems he's about to reveal Merlin's secret to Morgana, the Alator turns on his supposed ally and renders her unconscious. He then tells Merlin that he, and other hidden sorcerors, are willing to give their lives to help him.
Back at the castle, both Agravaine - who managed to once again avoid exposure as a traitor - and Arthur apologize to Gaius, who tells the boy king that Merlin-as-Emrys was not, in fact, the murderer of his father.
Merlin has pushed the limits of his strength to save Arthur, but even he may not be powerful enough to rescue Camelot€™s king.
In the battle foretold by the prophecies, all give their best, and Merlin wins the day.
Morgana may have one last trick up her sleeve to win the war.