Morgana has a nightmare in which Prince Arthur is drowning, as a beautiful young woman watches him die.
While Arthur is hunting with Merlin, when they hear a woman screaming. They rush toward the noise and see a woman and her father being attacked by bandits. Arthur shoots one with his crossbow and then duels by sword with the others. Merlin covertly uses magic to drop a heavy branch on one of the men. Arthur fells his opponent and turns to the last robber, who flees. The grateful woman says her name is Sophia, and Arthur is taken with her beauty.
Arthur brings them before Uther, where the father introduces himself as Aulfric, heir to Timor, and his daughter, Sophia. Uther notes they're a long way from home, and Aulfric explains that they'd been sacked by raiders and are traveling West to join other family. Much to Arthur's pleasure, Uther invites them to stay in Camelot for a while. Arthur instructs Merlin to give them a good room; Merlin notices he's smitten with Sophia. Mildly embarrassed, Arthur swears his intentions toward Sophia are completely honorable. Even so, he's easily convinced to put her in the room next to his.
Morgana is shocked to see Sophia, the woman from her dream, moving into the room next to Arthur's. After finding out her name through Merlin, she visits Gaius and tells him about her dream and, that Sophia is now staying at the castle. Gaius tries to reassure her that it's just her mind playing tricks, even though Morgana says she had the same dream where she saw Sophia at Camelot. Gaius gives her a stronger sleeping draught, as she said the one he prescribed isn't working well. He advises her not to tell Uther, under the guise of unnecessarily worrying him. However, Morgana isn't convinced that's the reason he's asking.
Aulfric returns to the forest to pay the only surviving robber, who asks for more money as all his friends are dead. However, Aulfric really didn't come to pay him anything. He points his staff, and his eyes turn red as he says casts a spell that kills the terrified robber. Meanwhile, Morgana has another nightmare about Sophia drowning Arthur.
The next morning, Arthur asks Merlin to cover for him so he can take Sophia riding instead of report to patrol. Merlin's resistant, fearing Uther will throw him in the stocks if he finds out, but Arthur cajoles him into it by first admitting he fancies Sophia, and second, by promising him he'll have a friend for life. As Morgana and Gwen (Guinevere) watch them ride off, Gwen encourages Morgana to tell Uther about her dream. However, Morgana fears he'd punish her for sorcery and decides to stop Sophia herself. Meanwhile, Merlin tells Uther he messed up Arthur's schedule and gets sent to the stocks for it.
Arthur shows Sophia around the forest, where she attempts to cast a spell on him. They're interrupted when the royal knights, thinking they're robbers, almost impale them with an arrow. Distracted by their approach, Arthur snaps out of it just in time to throw her to safety. After screaming at the guards, he apologizes to Sophia. When he hands Sophia her staff, she snaps at him not to touch it, then quickly apologizes, blaming her nerves. Arthur suggests they go back, but Sophia wants to continue to the river. Fearing more danger, Arthur insists they return to the castle, unknowingly foiling Sophia's plan.
Merlin comes home covered in food and tells Gaius that he covered for Arthur so he could take Sophia out for the day. Merlin says Arthur's besotted, surprising Gaius since they just met. Reminded of Morgana's dream, he sneaks into Aulfric's room and snoops through his possessions. He studies his staff, which is carved with odd writing, piquing his interest. Aulfric walks in on him and demands to know who he is. Gaius pretends he thought someone had broken in, and Aulfric says, "Looks like they have," his eyes reflexively flashing red with anger. Covering his shock at the sight, Gaius apologizes and leaves.
When Arthur and Sophia return from riding, Sophia goes to her quarters and runs into Morgana on the way. Sophia turns on the charm, but Morgana says she knows who she is and warns her to stay away from Arthur. Sophia tries to blow her off as a jealous rival, but Morgana stands firm, swearing to hunt her down if she harms Arthur.
Aulfric asks Sophia why she's back early. She explains she was almost killed. Instead of being grateful, she's humiliated that such a weak and feeble being saved her. Aulfric stresses the urgency of her mission; to get Arthur's heart so they can re-open the gates of Avalon and reassume their true forms. Sophia says she needs more time. Aulfric warns her to hurry, as the physician can see them for what they truly are. Sophia mentions her encounter with Morgana, whom she says fears her own powers but won't be quiet for long. They agree to complete the mission tomorrow, both looking forward to shedding their mortal shells.
Morgana tries to warn Arthur about her dreams, but he merely laughs her off, accusing her of being jealous. The next day, Arthur asks Merlin to cover for him again so he can be with Sophia instead of attending a knighting ceremony. When Arthur explains how smitten he is, Merlin agrees to do it. And again, gets thrown in the stocks. In the forest, Sophia casts a spell on Arthur to bring him under her control.
Merlin returns home, soiled with food and explains why to Gaius. Gaius says he shouldn't have covered for Arthur and tells him about Morgana's dream. He solemnly reveals that Morgana is a seer, something he tried to avoid admitting until now. He explains that Morgana, as a seer, can view the future in her dreams. He's kept this quiet to protect her from Uther, who considers the ability to be too close to magic. He tells Merlin about his encounter with Aulfric and fears that Arthur is in danger. In Arthur's room, Sophia seals the deal with a kiss, casting a love spell on Arthur. "Till death do us part."
Merlin overhears Sophia tell Aulfric that Arthur's under her power and tomorrow he'll do what they need. Pleased, Aulfric leaves to tell the elders. Merlin follows him to the river where he summons the Sidhe elders -- small fairies that fly around Aulfric. He asks for passage back to Avalon, but the lead elder says they'll continue to be exiled from Avalon since Aulfric killed another Sidhe. Aulfric, punished to be in a mortal body forever, begs them to let his daughter return. He says she can return if they sacrifice a mortal prince to the Sidhe elders. Aulfric tells them about Arthur, delighting the lead elder.
Merlin returns and tells Gaius what he saw. Gaius explains that Avalon is the land of eternal youth, which mortals get a glimpse of moments before death. Merlin says he saw it and is still here. Gaius is momentarily distracted by that and wants to know what it looked like, until Merlin reminds him they have to save Arthur. Gaius has identified the ancient script on Aulfric's staff as Orthanc, and says they must be Sidhe, masters of enchantment. He's certain Arthur has been bewitched.
Arthur asks Uther for permission to marry Sophia, which is not only denied, but laughed at until Arthur says he'll marry Sophia whether Uther gives him permission or not. At that, Uther threatens to have Aulfric and Sophia executed if Arthur continues to disrespect him. Arthur changes his tone and Uther releases them. Afterward, Morgana almost tells Uther about her dreams, but can't do it. Instead, she gives a weak warning that Sophia will break Arthur's heart.
As Arthur suits up in his armor to leave Camelot, Merlin tries to convince him that Sophia has bewitched him. However, Aulfric and Sophia enter and make sure Arthur doesn't fall out of the spell. Merlin says he saw him at the river and tells Arthur that they're magical beings who plan to sacrifice him. He knows it's futile when Arthur's eyes glow red. Aulfric points his staff at Merlin and knocks him unconscious against a wall with a powerful spell.
Morgana sees Arthur leaving with Sophia and Aulfric, and runs to Gaius in a panic. He assures her that he believes her and that she can't tell Uther about her dreams or he'll charge her with witchcraft. He convinces her to leave the matter to him, promising he knows someone who can help. Gaius finds Merlin and shakes him out of his stupor to tell him that Sophia and Aulfric have taken Arthur away. Still wobbling and only alive because of his magical power, he runs into the forest after them.
At the river, Aulfric tells Sophia he can't go with her to Avalon. Upset, she doesn't want to go, but Aulfric says if the elders don't get Arthur's soul they'll take hers instead. They begin the ceremony with Sophia leading the bewitched Arthur, who's dressed in full armor, into the lake. He sinks under as Sophia stands over him, just like Morgana saw in her dream. Upon reaching the river, Merlin sees them and notices Sophia's staff at Aulfric's side. He uses magic to summon it, then blasts Aulfric and Sophia to pieces with a spell fired from the point. He then swims into the river and pulls Arthur from the murky water.
In his chambers, Arthur wakes with no memory of his ordeal. Merlin and Gaius tell him he eloped with Sophia and wouldn't return to Camelot, so Merlin knocked him out and brought him back. Arthur's horrified that Merlin overpowered him and that he eloped with Sophia. He orders them to keep both embarrassing events a secret. In front of Uther, Merlin again takes the blame for Arthur missing patrol. Uther asks Merlin if he has a mental affliction, which Gaius says he's looking into. Uther says that's good, because otherwise they'll have a food shortage. Merlin laughs until he realizes he's going to the stocks again.
Morgana visits Gaius and says she isn't sleeping well, so he gives her another sleeping potion. After she leaves, Gaius tells Merlin he can never let her know about her gift because Uther might have her killed. Merlin asks if Morgana is "like him." Gaius assures him that no one is like him. Merlin asks if Morgana can use magic. "For her sake, I hope not." Gaius responds. That night, she's startled awake by another nightmare.