Cunning, charismatic and violent, the warlock Alvarr has a plan to reclaim a precious artifact from Uther's vaults - The Crystal of Neahtid. Uther has no idea what the crystal is for, but he keeps it carefully guarded. Alvarr knows he needs the help of a palace insider if he is to succeed, and he has his sights set on recruiting the king's ward.
With Mordred in his care, the renegade leader breaks into Camelot and makes for Morgana's chambers. But his presence in the palace has not gone unnoticed - Merlin has heard Mordred's voice his head.
Morgana is terrified to wake up with Alvarr's hand over her mouth, but her fears are alleviated as soon as she sees Mordred. Alvarr tells her Uther killed his parents and - like Mordred - he has been hunted by the king since childhood. It's clear that Mordred trusts Alvarr, so she decides to let her guard down. As Merlin alerts Arthur to the intruders' presence, Alvarr tells Morgana that Uther stole something from the druids many years ago, and it's time they had it back. Arthur and his guards burst through the door but, by then, the room is empty and Morgana insists she is alone. Arthur is apologetic, but Merlin eyes Morgana suspiciously.
Later, the warning bell rings out. Arthur and Uther are horrified to find that The Crystal of Neahtid has been stolen. Merlin goes to the Dragon, but the great creature refuses to answer Merlin's questions about the crystal until the young warlock honours his promise to free him. Merlin stalls, promising that, once this mess is over, he will do so. The Great Dragon explains that to those with the right power, the crystal can provide the secrets of the past, the present and the future. Merlin tells him that Morgana has it, and the Dragon scoffs - Morgana won't have the power to wield the crystal. Mordred, on the other hand, just might.
Later, Morgana sneaks out of the castle. Merlin follows as she makes her way to the Forest of Chemary. He watches, disturbed, as she meets with Alvarr and Mordred and hands over the crystal. Alvarr calls her a hero. It is his hope that Mordred will be able to harness the power of the crystal, and then those with magic will be more powerful than any army in the land. Morgana's alarmed at the thought of other people suffering, but Alvarr insists that there are no half measures, and assures her that she is no longer alone. He knows of her magic, and he thinks her very. These words work like magic on lonely, haunted Morgana. Alvarr kisses her and, enthralled, she doesn't pull away.
Merlin returns to Camelot and tells Gaius what he has witnessed. Gaius has a plan. The next morning, he tells the King all about Alvarr, but leaves both Morgana and Merlin out, claiming that the information came from an innocent witness whose identity must be protected. Accepting this, Uther orders Arthur to take a group of men to the Valley of Chemary.
As Arthur and Merlin prepare for their trip, Morgana once more risks everything to slip out of the castle and warn Alvarr. By the time Merlin and Arthur reach the camp, the renegades have set a trap. A vicious battle ensues. In the middle of the fray, Merlin spots Mordred and realises this is his chance to defy the prophesy of Arthur's doom. He chases the boy and uses magic to bring down a tree branch and trip him up. The boy scrambles to defend himself, killing two knights who attack him. Steely, Mordred tells Merlin that he will never forget this betrayal, before darting away into the trees.
Arthur and his knights prevail, capturing Alvarr and retrieving the crystal. Alvarr remains defiant, telling Arthur that there is little point him having the stone - no one in Camelot has the power to wield it.
But that night, as Arthur and his men sleep, Merlin examines the crystal. Suddenly he is overwhelmed by a vision - the Great Dragon attacking Camelot. Merlin is horrified and hastily stuffs the crystal away. Gaius tries to reassure Merlin that the version of the future he saw in the stone won't necessarily come to be, but the young warlock remains unsettled, privately recalling his promise.
Uther convicts Alvarr of treason and sentences him to death. Cold with rage, Morgana tells the king that, from this day forward,she disowns him. Uther is shaken by her condemnation, but stands firm. That night, Morgana presents Alvarr's prison guards with a flagon of brandy laced with one of Gaius' sleeping draughts. She tells Alvarr that she has eased the way for his escape. He busts out of his cell with magic and flees Camelot. Uther is furious, aware that someone inside the castle has betrayed him.
That night, Merlin cannot sleep. The Great Dragon cries out to him in anger and frustration, reminding him of the promise he is yet to honour. Merlin pulls his pillow tightly over his head - after what he saw in the crystal, he refuses to listen.
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