The Mark of Nimueh

"This is magic of the darkest kind."

- Gaius

The Mark of Nimueh is the third episode of the first series broadcast on 4 October 2008. It marks the first appearance of Nimueh, the main antagonist of series one.

Plot
A mysterious sorceress sculpts a tiny creature from water and clay, places it inside an egg, and brings the creature to life with a spell. She deposits the egg in the basin of a scrying fount, directing it magically through an underwater route into the river that supplies Camelot with water. The egg surfaces inside a vault beneath the castle, and hatches.

Gaius and Merlin tend to a man who has died from an unknown pathogen, covering the corpse with a sheet so as not to alarm the townspeople. Guinevere encounters them while taking flowers to Morgana Pendragon and gives Merlin one of the blossoms. Prince Arthur Pendragon arrives at the physicians quarters for Merlin and summons Gaius to appear before the king.

One of the royal court servants has died from the same disease that killed Gaius's dead patient, and King Uther Pendragon demands to know what Gaius has discovered. Pressured for answers, Gaius admits that sorcery is the most likely cause, and Uther orders Arthur to conduct searches of every house in town while Merlin is assigned to Gaius until the illness is explained.

Merlin cannot understand why anyone would want to harm others with magic; Gaius explains that the power of magic can corrupt those who wield it, but that magic itself, being a tool, is neither good or evil. Their investigations are interrupted by Arthur and his guards, who search the quarters, including Merlin's room.

Merlin panics because the book of magic is upstairs, but he manages to hide it while Arthur is distracted. After Arthur leaves, Merlin becomes angry that Gaius will not let him use magic to help the victims, but the physician insists that the only way to help is to discern the source of the plague. He tells the frustrated boy that Merlin's time to be a great sorcerer will come.

When Arthur fails to find any evidence of sorcery in town, Uther commands him to search the outer regions of the country, impose a curfew, and isolate the lower section of the city where most of the victims lived. Elsewhere, Merlin and Gaius deduce that the plague is not spread through physical contact, as a royal courtier would not have been near the lower city, and that the only similarity between the victims is the water they drank. Meanwhile, Gwen's father Tom has contracted the plague, and Gwen begs Gaius to save him, running away in tears when Gaius tells her there is no cure. That night, Merlin uses his magic to evade the royal guards and travels to the lower city to cure Tom by placing a poultice under the blacksmith's pillow and magically releasing a medicinal vapour.

Gaius later tells Uther that the contaminated water comes from the pump which supplies the city. Merlin feigns surprise when he hears from Gwen that her father has recovered, but she remains suspicious of his reaction, yet laughs off his claim of being psychic. Arthur soon hears of Tom's recovery, and learns that Gwen had been the only person with him while he lay on his death-bed; his house is searched, and Arthur's men find the magical poultice. Arthur is forced to arrest Gwen for sorcery and delivers her to the king, who promptly blames Gwen for the illness and orders her to lift the curse. Having no magical ability, she insists that she can't, but Uther accuses her of lying and sentences her to death. Arthur and Morgana argue for her innocence, claiming that, even if Gwen used sorcery to heal her father, she has no evil intention in her nature. Uther ignores them.

Merlin visits Gwen in the dungeon where she is being held, and promises not to let her die. He then interrupts the King's council and confesses to using sorcery to cure Tom; Arthur intervenes, persuading the King and his advisors that Merlin is so in love with Gwen that his thoughts are clouded, and a amused Uther dismisses the apprentice without punishment. Merlin and Gaius later take a sample of the water inside the vault beneath the castle and discover an Afanc, which Gaius explains can only be created by the most powerful of sorcerers. Merlin returns to the Dragon's cave to seek the counsel of The Great Dragon; he is told to use the elements available to him, and that he and Arthur are two sides of a coin. Uther, desperate to stop his people dying, moves Gwen's execution forward to that evening.

With help from Gaius, Merlin works out that since clay is made from two of the four Elements – earth and water – he may be able to stop the Afanc by countering with the opposite two elements – air and fire. He utters the spell: "Lyft sy þe in bǽlwylm ac forhienan se wiðere!", which means "You are air in fire's heat but defeat the hostile one".

Morgana arrives to inform them that Gwen is to be executed that evening, and accompanies Merlin and Arthur as they descend back down to the vault to face the Afanc. They pursue the creature through the caves until Arthur corners it, killing it with the flame from his torch and a spell from Merlin that conjures a fierce wind. The mysterious sorceress watches all of this through her scrying fount, and curses Merlin for ruining her scheme.

Later, Gaius delivers to Uther the shards of the egg from which the Afanc hatched, showing him that they bear the mark of Nimueh. Uther is exceedingly dismayed by the news, lamenting: "will I never be rid of her?" Gwen is released from prison, and Morgana tells Merlin that she knows "his secret," which is safe with her. Merlin is initially relieved that he can confide his magical abilities in someone other than Gaius, but looks crestfallen when he realises that Morgana merely believes that Merlin harbours a "secret" affection for Gwen, who she calls "a very lucky woman."

From her refuge, Nimueh swears revenge on Merlin.

Main Cast

 * Colin Morgan as Merlin
 * Bradley James as Prince Arthur
 * Richard Wilson as Gaius
 * Anthony Head as Uther Pendragon
 * Angel Coulby as Gwen
 * Katie McGrath as Morgana Pendragon

Recurring Cast

 * John Hurt as the voice of The Great Dragon
 * Michelle Ryan as Nimueh
 * David Durham as Tom

Guest Cast

 * Rick English as The Afanc

Release & Reception

 * The Mark of Nimueh premiered on Syfy UK at 7pm on September 7th 2017, immediately followed by The Poisoned Chalice.
 * The episode received 5.76 million viewers (28.9%), which is an 800,000 rise from the previous episode in a 7:05pm time slot.
 * The episode along with the previous two will be on the first volume of Merlin released 24 November 2008.