A convoy heading for Camelot is ambushed by bandits in the forest outside the castle. The knights guarding the convey are wiped out and the bandit leader, Alvarr, has his men steal and wear the armour and clothing of the knights. He tells a hooded figure watching him they will have to hurry if they want to make Camelot before nightfall. The figure nods and removes its hood, revealing himself to be the druid boy, Mordred.
The bandits, Alvarr and Mordred reach Camelot that night and sneak into the city. Mordred telepathically guides Alvarr and himself to Morgana's chambers: however, their conversation is overheard by Merlin, who goes to investigate. The pair reach her chambers and wake her: Morgana is delighted to see Mordred, but says they risk much by coming to Camelot. Alvarr explains he and his men are ready to fight against Uther, and that all they need now is a weapon powerful enough to achieve victory. He explains they are seeking a crystal of great power, taken by Uther in the Great Purge and hidden in the vaults of Camelot. When Morgana says Alvarr could never get it out of the vaults, Alvarr agrees that he can't...but she can.
However, by this time, Merlin has raised the alarm, and storms into Morgana's chambers with Arthur and the guards. However, Morgana is seemingly alone and she orders them out: Arthur angrily leaves, berates Merlin for wasting his time and storms off. When they are gone, Alvarr and Mordred emerge from their hiding places and beg Morgana for her help: she reluctantly agrees to help them. The next day, Merlin tells Gaius what happened that night, of Mordred's presence and the fact that whatever he and Alvarr were searching for in Camelot, they were prepared to die for it. Later that day, Morgana sneaks into Arthur's chambers and steals the keys to the vault, narrowly managing to evade Merlin's suspicions when he finds her there. She heads down to the vaults and steals the crystal.
Uther is furious to learn the crystal (or the Crystal of Neahtid, as it is truly called) has been stolen and orders Arthur to find it immediately. When Arthur asks why it is so important, Uther admits he doesn't know, but points out that several sorcerers died to protect it during the Great Purge means it must be important to them. In private, Merlin tells Gaius that Morgana stole the Crystal: however, since they have no proof, they cannot take their suspicions to Uther. Gaius says there are many legends surrounding the Crystal, and that it is supposed to contain the secret of time itself. However, Gaius admits he doesn't know much, and that there is only one alive who would more...
Merlin goes to the Great Dragon, who upon seeing Merlin demands to be set free. Merlin asserts that he will, only when he is certain Camelot is safe. Clearly disappointed, the Dragon relents, and answers Merlin's questions regarding the Crystal: whoever controls it will know all about the past, present and future. The Dragon laughs when he hears Morgana has stolen the crystal, sneering that she won't know how to use it, but when Merlin mentions Mordred, he grows worried: the Dragon admits Mordred could use the crystal, and not only reminds Merlin of the boy's destiny to destroy Arthur, but tells him of an ancient prophecy that tells of Morgana and Mordred, united in evil and warns that this must be stopped...at any cost.
That night, Morgana flees Camelot with the Crystal and goes to Alvarr, followed by Merlin. She gives Alvarr the Crystal, who tells her once Mordred has mastered its use, they will destroy Uther and Camelot. The charismatic Alvarr charms Morgana to his way of thinking, and she agrees to their plans, before returning to Camelot. Merlin returns to Gaius and tells him all that has happened: Gaius is quite unnerved, since Alvarr is a formidable sorcerer and has threatened to destroy Camelot before. Merlin remarks he has a fanatic who has already swayed so many, including Morgana and Mordred to his cause. The pair tell Uther of this, but leave out Morgana's part to protect her from Uther's wrath. Arthur is ordered to travel to the camp and investigate.
Morgana, however, heads to Alvarr's camp and warns him of Arthur's approach. When Arthur, Merlin and the knights arrive at the camp, they are ambushed by Alvarr's men, and a vicious battle ensues. In the confusion, Merlin sees Mordred trying to flee: remembering the Dragon's warning, Merlin uses magic to trip Mordred, leaving his vulnerable to two soldiers. However, Mordred uses his own magic to throw spears at the soldiers, killing them. Before he runs to safety, Mordred glares at Merlin, and telepathically snarls that he will neither forget nor forgive this betrayal. Arthur and his men soon defeat Alvarr's men, take him prisoner and recover the Crystal. That night, Merlin takes the Crystal while Arthur and the knights sleep and looks into it: he sees a terrible vision of the Great Dragon laying waste to the city, and knows that it would be his fault. Horrified, Merlin casts the crystal away.
Alvarr is tried in Camelot and sentenced to death by Uther. Still in Alvarr's thrall, Morgana berates Uther in private, hatefully denouncing him as an arrogant fool who ignores the needs of the people he claims to protect, and is hated as such by them and her. Furious at these accusations, Uther tells Morgana to go to her chambers, to which Morgana spitefully retorts "And you, Uther, you will go to Hell!", a pronouncement that clearly leaves Uther stricken. That night, Morgana drugs Alvarr's guards with her sleeping draught and helps Alvarr to escape. When Uther hears this, he furiously vows that if he ever finds out who aided Alvarr, they will rue the day they were born, glaring coldly at Morgana as he says this. Morgana returns his gaze and smiles coldly to herself as she leaves, confirming to Merlin that she was responsible.
Merlin confesses to Gaius that he looked into the Crystal and saw the terrible future it predicted: however, Gaius consoles him that what he saw was only one possible future, and that the future has not been shaped and that they all have the power to change it. However, that night, the Great Dragon speaks into his mind, demanding to be set free. Merlin is left in agony as the Dragon telepathically bellows at him, torn between his desire to honour his promise, and his fear of what may come to pass if he does.