On a picnic for Arthur and his newly restored queen, Merlin finds a fine metal clasp made in the town of Helver. On returning to Camelot, he discovers that hundreds of refugees from that same town are in the citadel. Merlin returns to the spot, knowing that magic was at work, and finds evidence that Morgana attacked Helver in order to capture Alator, Merlin's onetime protector and keeper of his secret. Later, on an errand for Arthur, Merlin is confronted by a woman who calls him by his true name, and urges him to meet her in secret at midnight. Merlin promises Gaius he won't, but the physician doesn't believe him and tells Arthur of the sorceress's presence in Camelot. Arthur dispatches a search party while Merlin slips away in secret.
The woman, Finna, warns Merlin that the battle for Camelot - and Arthur's life - draws near. As she is about to tell him how to win, Arthur's knights approach. They split, with the promise to find each other later. Meanwhile, a letter that Finna sent to Alator in Morgana's prison is discovered - Morgana now knows of Finna's existence, and after killing Alator, begins her search for the sorceress. Merlin is also looking for Finna, but Arthur's knights find him first, and though he protests that he's looking for herbs for Gaius, the knights won't let him leave. He sneaks away in the night, spied only by Mordred, who gives him his blessing and says he'll make an excuse to the other knights.
Merlin and Finna meet once more, but Morgana is on their trail and her Saxon warriors land an arrow in Merlin's flesh before Merlin dispatches them all. He and Finna limp forward to a ruined citadel, their only object to keep Morgana from learning Emrys's true identity. Behind the stone walls, Finna hands Merlin a sacred object - a box containing a scroll - and has Merlin vow never to trust Mordred. She then orders him to run to the roof and leave her to face Morgana. Finna stabs herself in front of Morgana in order to keep her from finding out who Emrys is. Once the soldiers retreat, Merlin calls upon the dragon, who carries him away and heals his wound with his ancient magic. The dragon is growing old, and Merlin feels the time is coming soon for him to stand alone. The young warlock feels unable to do so, but presses on.
Merlin returns to Camelot where Gaius reads Finna's scroll, a prophesy that foretells Arthur's death on the battlefield of Camlan. Merlin feels weak and unsteady, but Gaius reassures him that if anyone can lead Arthur and the kingdom to its destiny, it's him. They are interrupted by a death bell that brings a knight disfigured by a spell that caused the skin of his face to grow over all of his features and suffocate him. The knight's death is a clear declaration from Morgana: They are at war.