Arthur, Merlin and the Knights are ambushed by mercenaries when they attempt to take a shortcut through the Valley of the Kings. Merlin takes a blow to the chest and Arthur helps move him to a safer location where they both can hide. Under the cover of the night, Merlin and Arthur try to make the situation a bit more lighthearted, talking of heroism and cowardice. When they wake in the morning, Arthur hoists Merlin over his shoulders, hoping they can outrun the men chasing them. Unfortunately, they are pinned in a narrow passageway, forcing Arthur to put Merlin down and fight. Merlin does what he can to ensure Arthur’s safety by causing a rockslide, but he is now alone and injured.
The mercenaries, led by Agravaine, bring Merlin to Morgana. At first, Morgana’s none too happy about seeing Merlin and not Arthur at her feet. She manages to turn that around by finding a way to use Merlin to her advantage. With him chained up in her hut, Morgana informs him that she does not plan on killing him. Merlin questions her motives for patching him up and keeping him around as she wonders why he is so loyal to Arthur. When Merlin replies accusing her of a lack of duty and loyalty, Morgana picks up an ancient engraving, calling forth a Formorroh, a seven-headed snake demon. She removes one of the heads and inserts it into the base of Merlin’s neck. She explains that the Fomorroh will take over Merlin’s mind, making him her puppet, her tool to kill Arthur.
The Fomorroh
Arthur meets up with the Knights, but no one has seen Merlin. When they return to the castle, Arthur asks Sir Leon to send out patrols to scour the forest, and the King promises Gaius that they will find him. Leon and Agravaine report back that there is no sign of Merlin. Agravaine keeps trying to throw suspicions on a neighbouring kingdom, but Arthur does not take the bait. They come to the conclusion that there must be a traitor amongst his inner circle.
The following morning, Arthur finds he has a new servant named George standing at the foot of his bed. He’s as far from Merlin as one could get, polite, a real go-getter, and very serious about his position as King’s man servant. But Arthur refuses to believe Merlin is gone, and against Gwen’s wishes, he heads out to search with Gwaine. They happen upon Merlin, covered head to toe in mud, in the ditch where Morgana left him with no memory of what she did to him.
Gaius immediately senses something wrong with Merlin, but can’t quite put his finger on it. Merlin avoids telling him just how he escaped, and then starts asking about poisons. Merlin’s first attempt to kill Arthur under Morgana’s control is to poison his meal. However, Merlin enters the King’s chambers with his deadly plate of food only to find that Gwen has already brought lunch. Puppet Merlin is pretty upset about it, saying some nasty things to Gwen and generally behaving like a jerk. He tossed the uneaten meal into a pigpen on his way back home.
Planning his next move, Merlin paces to and fro in the main quarters, once again bewildering Gaius. After turning down aid from his mentor, Merlin heads to the armory where he runs into Leon. Puppet Merlin asks Leon what sort of crossbow the knight would use if he wanted to hurt something. Leon takes down a gorgeous bow from the wall, and asks what Merlin wants it for. Merlin replies it’s to kill Arthur, and Leon laughs it off as a joke. Merlin takes it to Arthur’s room and sets it up to trigger when the wardrobe is opened. His test run is successful, but interrupted as Arthur enters the room to prepare for a knighting ceremony. Arthur thinks the ceremony is a waste of time knowing there is a traitor that wants him dead, joking that it may even be Merlin.
In the market, Gwen passes the pigpen where Merlin discarded the poisoned meal. A crowd has gathered because the animals have died. Gwen recognizes the plate and remnants, getting Gaius involved as she is concerned. They share their observations of his peculiar behaviour, and Gaius suspects something has happened. They head to the castle to find Merlin, coming across Leon, who tells them about Merlin and the crossbow. Merlin is in Arthur’s room helping him get dressed for the ceremony. Arthur is distracted with who the traitor could be, going through the list of his Knights looking for reasons. A frustrated Merlin opens the wardrobe when Arthur goes behind his folding screen and nearly takes an arrow to the chest. With the crossbow out of the question, he decides to uses Arthur’s ceremonial sword. Right as he has an opening with the King’s back turned, Gwen and Gaius enter the room and watch as Merlin’s running attack misses when he runs into a pillar in the room. Arthur picks up his sword and leaves, at which point Gwen picks up a silver pitcher and whacks Merlin in the head so they can get him back to Gaius’ place without incident.
Arthur pays a visit to his uncle, explaining that he does not take the issue of a traitor in the castle as lightly as Agravaine is. His investigation have caused him to hold doubts against his uncle. Agravaine hopes to cover his intentions by casting doubt once more on Gaius. When he has the chance, Agravaine returns to Morgana telling her he’s setting Gaius up to be the traitor. She’s still not completely impressed, but lets him leave with his head.
Awkwardly Naked Arthur
Gaius deduces that Merlin has been placed under the spell of a Fomorroh. He uses his skills to paralyze and remove the head from Merlin’s neck. He tosses it in the fire, believing that Merlin is now free from the spell. When Merlin wakes up, Gaius thinks Merlin simply just doesn’t remember what happened. But as Merlin gets ready to head out, we see that the Fomorroh head is back at the base of his neck. Merlin heads to Arthur’s room and prepares the King’s bath. He pours in a container of white powder that turns the bathwater to acid and eats away the sword Merlin uses to test it. Gwen and Gaius walk in in the nick of time, and once again Gwen belts him with the pitcher. She lies to Arthur, telling him the water is cold and that Merlin’s gone to fix it, but he won’t be able to have a bath today. An awkward situation as he stands in front of her and Gaius covering himself with a pillow.
Gaius and Gwen minister to Merlin, now aware that you simply can’t just kill a Fomorroh head. Gaius numbs the new head, then wakes Merlin up to talk to him. Merlin remembers Morgana conjuring the snake, but nothing afterward. The only way Gaius knows to get rid of the snake permanently is to destroy the entire beast. Merlin heads off to Morgana’s hut disguised as Old Merlin. Shortly after drinking the potion that makes him appear old, he tries to get back on his horse and Leon, Gwaine, Percival and Elyan stumble on the hilarity. The men remember how he escaped his burning on the pyre and plan on taking him back to Arthur. Merlin uses his magic and knocks them out, making a step ladder for him to use to mount the horse.
"Old" Merlin needs assistance
Merlin watches from a distance as Agravaine and Morgana leave her hiding spot, waiting until he’s clear to enter himself. He rummages around, not noticing Morgana slipping back in and observing him. Their eyes meet, Morgana’s face filled with fear and denying his existence, believing that he is Emrys. He finds what he’s looking for, the Formorroh hidden in a jar, tells Morgana she’s right, he isn’t real, then throws her with magic into the shelves behind her. She chases him outside and the two have a small fight using magic. When Morgana thinks she won, she collects the jar and walks away, but Merlin isn’t done yet. He summons a whirlwind which picks her up and throws her to the ground. With her out cold, Merlin starts a fire and destroys the entire Fomorroh in it.
Gaius removes the now dead snake head from Merlin’s neck, and Gwen comes to collect him for Arthur. Arthur believes that Merlin spent the last two days in the tavern, Gaius’ go-to explanation for the King whenever Merlin is off doing something. Merlin argues that Arthur wouldn’t get rid of him because who else would clean his armor or get his food. That’s when Merlin is introduced to George and handed over for training.
The episode ends with Agravaine finding Morgana’s home trashed and coming across her unconscious body outside.
Box sets for Season One , Season Two and Season Three of Merlin are now available to purchase in the US via Amazon