It is a dark night in a small village, where a man and wife are getting ready for bed inside a small cottage. They hear a scream somewhere outside and the man goes to investigate, hearing a hissing noise in the darkness and finally stumbling into a man that looks comatose. Something in the bushes darts away out of sight.
Back in Camelot, Gwen is folding linen in her house when she hears a knock at the door. The woman from the village is there, revealed to be an old friend of Gwen, who has come to her for help.
Gwen takes Mary to Arthur, and he hears her story: that in the village of Longstead there is a strange affliction that has affected several of the men. With no physician, the people donít know what to do. Arthur promises her all the help he can give.
Down in the physicianís quarters, Gaius is busy with patients that have the sweating sickness, and suggests that Merlin go in his place. Arthur is skeptical, but Gaius vouches for his capabilities as an observant physician-in-training.
Over dinner, Merlin questions Gaiusís decision.
Merlin: Do you really think I can do this, Gaius?
Gaius: I know you can.
Merlin: Iím not a physician, I donít have anything like the knowledge you do.
Gaius: Youíve been working for me for many years, Merlin, I suspect you know more than you think you do.
Merlin: I just do what you tell me to do, I donít have to make the decisions myself. These people would be putting their lives in my hands.
Gaius: I put my life in your hands every day, Merlin. As does Arthur and Gwen and all of Camelot, though they may not know it. Youíre the one who holds the fate of this kingdom in the balance.
The following morning Merlin packs his belongings and Gaius presents him with his medicine bag filled with supplies. Merlin thanks him, and Gaius looks back at him with complete confidence.
Merlin, Guinevere, Mary and the knights gallop out from Camelot and through the forests until they reach Longstead. Guinevere and Mary meet her husband John, who is pleased at their return, but somewhat disappointed by how young Merlin looks. Elyan and Gwen stick up for him, and Merlin is taken to see the patients. He looks over them and waits until John and Gwen have left before using his magic on the bodies, looking disconcerted when it has no effect.
Reading through a book of medicine that night, Merlin hears a hissing noise from outside and goes to investigate with a fishing rod as a makeshift weapon. He raises it to strike something moving around the corner, only to find Gwaine on the way back from a call of nature. They laugh together, but Merlin hears the hissing one last time before returning inside.
By morning the patients are unchanged, and Merlin recommends returning to Camelot in order to fetch Gaius. John suggests that it might have been sorcery based on his experiences of the other night.
Merlin, Gwen and the knights ride from the village and through the forest until Leon stops them, having seen campfire smoke in the distance. The group creeps toward it, discovering a group of bandits. They plan to bypass them without being noticed until Gwaine notices that they have a frightened girl held captive, and leaps into battle. Each knight uses their own specific fighting skills to dispatch the bandits, and even Merlin takes one out with his discreet use of magic. The remaining bandits flee and the knights discover Percival behind a tree, cradling the unconscious girl.
Merlin reaches forward to check her and she awakes with a scream at the touch of his hand. Percival reassures her, and Gwen introduces herself as she unties her hands. In return, the girl tells them that her name is Lamia, though she still shies away from Merlinís touch.
Walking through the forests with Lamia on horseback, Leon announces that they should make camp. Merlin tries to help Lamia from the saddle, but she flinches. Angrily, Percival shoves him away and lifts Lamia down himself. Gwen tries to excuse him, but Merlin looks rather uneasy.
By night Percival is on watch and hears Lamia crying. He comforts her with a hug, but her eyes glow green. Before she gets the chance to do anything, both are startled by Merlin approaching with a flagon of water to offer her. Percival walks off with Lamia without a word.
Back in Camelot, Arthur is getting worried about the partyís prolonged absence. Though Agravaine tries to reassure him, Arthur announces that he and Gaius will be leaving at first light Ė and so they do, with a guard of Camelotís knights.
Lamia rejects a bowl of food that Gwen has prepared for her, but both she and Merlin are surprised when Leon announces that they are riding east in order to take Lamia to her village. Merlin insists that they return to Camelot to fetch Gaius for the people at Longstead, but though Gwen backs him up, the knights silence both of them.
Arthur and his convoy are trotting through the woods when Arthur stops them, noticing that there are no birds in the trees. A knight calls him over to where are group of men are lying dead around an abandoned cart. Arthur asks Gaius if he notices anything strange about the bodies. Apart from the fact that theyíre all wearing bright purple neckties, Gaius points out that there are no wounds on them.
Gaius notices scratch-marks on the side of the cart, and one man is found still alive among the corpses.
Back with the knights, Leon is preparing to give Lamia a water flask when Gwaine grabs it and tries to do it himself. They are soon shoving each other and despite Merlinís intervention, draw their swords. Percival and Elyan race in to separate them, and Lamia watches with a little smile on her face as Leon is wounded.
Arthur has reached Longstead to learn that the knights rode out for Camelot yesterday morning. Gaius is looking over the sick men and confirms Merlinís suspicions that their illness is based in sorcery.
Together Gwen and Merlin have stitched and bandaged Leonís wound, and have a quiet conference about how strange theyíre all acting. Merlin confides in her that the girl may be responsible, but neither are sure how sheís doing it.
Back in Longstead, Gaius has spoken to the injured man. He was a slave-trader who was travelling with the girl, blaming her for the quarrels that broke out among them on the way. She broke free and killed them all, and Gaius has her pegged as a lamia. They were created by the high priestesses of the old religion, mingling the blood of a girl with that of a serpent, that can control the minds of men and suck out their life-force with a kiss. The high priestesses lost control of their creations, which can also transform into hideous monsters.
Back at camp, Elyan hears a hissing noise and goes to investigate, running across Lamia. She approaches him slowly and kisses him, her eyes glowing green as he falls to the ground.
Merlin, Gwen and the knights wake up to find Elyan missing. Gwen is told to stay with Lamia as the men split up to look for him, and Lamia rather sinisterly tells Gwen that her brother will be found soon enough.
Agravaine is looking increasingly impatient with Arthurís search for the missing knights, but says nothing as they head deeper into the forest. Meanwhile, Leon and Percival return with an unconscious Elyan, and Gwen rushes to Merlinís side, agreeing with him that Lamia is responsible. As Merlin insists that they return to Camelot, Lamia stands and says that she can lead them to shelter in a nearby castle. Though Merlin and Gwen argue against it, Leon yells at them and follows Lamiaís lead.
On horseback, Merlin and Gwen quietly plot among themselves, reasoning that Arthur will have realized that somethingís wrong and will be on their trail. Sure enough, Arthur and his knights are searching the ground for clues, and Gwen ties a scrap of her tunic on a tree branch in order to mark their passage. Though Agravaine covers up some of the tracks that they come across, Arthur finds the scrap of cloth and recognises it as Guinevereís.
Merlin, Gwen and the knights follow Lamia with flaming torches and an unconscious Elyan into the bowels of the castle. Merlin tries to warn Percival, but is only threatened in return. As soon as theyíre in the tunnels beneath the castle, the torches die out and by the time Merlin has secretly reignited them with magic, Lamia has disappeared.
They enter a large room filled with skeletons, and Leon orders that they find Lamia. Merlin insists that Lamia is dangerous, and when Leon attacks him in anger, Gwen breaks up the fight by insisting that they find somewhere warm for Elyan.
The knights deposit Gwen, Merlin and the unconscious Elyan in a small room and then spread out to look for Lamia. Gwaine breaks up a crate in order to make a fire, and even he is getting aggravated with Merlinís insistence that none of them are safe. Gwaine leaves to find more wood, and Gwen tearfully says that Elyan wonít make it unless he gets help soon.
Gwaine, Percival and Leon hunt through the castle, running across skeletons and hissing noises as they go.
Back in the small room, Gwen asks Merlin why it is that the knights have been enchanted while they have been spared.
Gwen: I donít understand it, why have only the knights been enchanted? Why not us as well?
Merlin: Youíre a woman.
Merlin: All the victims have been men.
Gwen: So why havenít you fallen under her spell?
Merlin: Iíve just been lucky, I suppose.
Gwen: There must be a reason.
Merlin: Maybe itís because Iím not a knight.
Gwen: The three villagers werenít knight either.
Merlin: Who knows?
Gwen: No, thereís something about you Merlin. Itís the way she looks at you, as though you were the enemy.
Just then they hear a scream, and telling Gwen to stay put, Merlin heads out to investigate. He follows the hissing noise, and comes across an unconscious Gwaine.
Arthur and Agravaine are still following the trail that Gwen has left, and soon come across the abandoned castle.
Percival finds Lamia weeping once more, and turns her around. Thanking him, she leans forward to kiss him. Leon arrives just in time to see Lamiaís eyes growing green and Percival falling to her feet. He attacks Lamia, only for her to telekinetically throw him across the room. At that point Merlin shows up, seeing her leaning over Leonís body, and despite a Badass Boast
, is also thrown across the room. He uses magic to levitate a sword into her stomach and she disappears behind a wooden beam. As Merlin rushes to check on Leon, she reappears as some sort of giant octopus thing.
Merlin runs for it and attempts to ward her off with falling masonry, but she only bursts her way through the stones that block the entrance to the room. Elsewhere, Gwen jumps at the sound and grabs Elyanís sword to investigate.
Merlin is racing through corridors when Gwen appears, sword in hand. Merlin grabs her and pushes her ahead of him, only for the lamia to wrap a tentacle around his ankle and pull him toward her. Gwen musters her courage and runs toward the monster, stabbing it twice before falling to the ground beside Merlin. The two of them begin to crawl away, and Merlin is just about to use his magic against it when it shrieks in pain and collapses. Right behind it is Arthur, having thrown a spear into its back.
Gwen jumps up and runs into his arms for a hug, Arthur helps Merlin get to his feet, and the three of them head off to help the other knights.
Back at the village, the men are recovering from their ordeal under Gaiusís care. Arthur shakes Percivalís hand and heads outside to tease Merlin about the fact that he was saved by a woman.
Back in Camelot, Gwen joins Arthur in his study.
Arthur: I thought I knew everything about you, Guinevere. Your loyalty, your wisdomÖsince when did you become this fearless hero?
Gwen: Well, maybe you just didnít notice before.
Arthur: Mm, maybe I didnít.
He takes her hand.
Arthur: Truly. You showed great courage back there.
Gwen: I did what anyone else would have done.
Arthur: You did a great deal more than that; you were equal to any knight of Camelot. Iím proud of you.
- Absentee Actor: No Morgana in this one, though as far as wicked females go, Lamia picks up the slack.
- Actor Allusion: Melanie Hill who plays Mary the villager appeared in Stardust as Ditchwater Sal. That movie also had a villainess called Lamia.
- Adaptational Villainy: Some stories about creatures called lamias do not neccesarily portray them as evil.
- Ankle Drag: Lamia grabs Merlin this way with one of her tentacles.
- Antagonist Title
- Beware the Nice Ones: Lamia finds out what happens when Merlin and Gwen get riled.
- Big Damn Heroes: Arthur (and the assorted knights behind him).
- Bitch in Sheep's Clothing
- Brainwashed and Crazy: The knights.
- Charm Person: Lamia
- Combat Tentacles: Lamia, in her monstrous form.
- Conveniently Timed Attack from Behind: Arthur arrives just in the nick of time to save Merlin and Guinevere from Lamia. Of course, it is a slightly variation on the trope considering Merlin and Gwen weren't in a huge amount of danger — Arthur technically only saved Merlin from the need to expose his magic in front of Gwen.
- Eldritch Abomination: Lamia's true form.
- Exploring the Evil Lair
- Family-Unfriendly Aesop: Bros Before Hoes.
- Filler: Unless they bring up Gwen's suspicions about Merlin again, this will be the only episode this season that was not part of an arc or might be relevant in future episodes.
- Forgot Flanders Could Do That: Arthur expresses delight at the fact that the usually passive and demure Guinevere is, if not skilled, at least competent in defending herself and others from harm. This is less of a surprise to viewers, who knew about her capabilities as far back as 1x10.
- Huge Guy, Tiny Girl: Lamia and the knights, particularly Percival.
- Mama Bear: Do not mess with Merlin if Gwen's around! Heck, she remains relatively calm even after her own brother is attacked, but when Merlin is threatened? Stabbing will ensue.
- Monster of the Week: Lamia.
- One-Gender Race: There were only ever female lamia, according to Gaius.
- Risking The King: For the first and only time in the entire series, Arthur does the sensible thing and sends his knights out to investigate the trouble rather than going himself. (Of course, this is averted later when he goes in search of his missing servant, girlfriend and team of knights).
- Supernatural Is Purple: Lamia's purple dress.
- Trail of Bread Crumbs: Gwen leaves strips of her tunic behind for Arthur to follow.
- Twirl of Love: After Arthur kills the Lamia, the first thing Gwen does is jump up and leap into his arms.
- Wounded Gazelle Gambit: How the Lamia caught the Knights and put them under her spell.
- The Vamp: Lamia, of course.