The disguised sorceress then warns Merlin, blaming Bayard. While Camelot prepares to celebrate peace with Mercia's visiting ruler Bayard, Nimueh forges a poisoned chalice and replaces it with one due to be given to Arthur. With some prompting from Morgana, Arthur goes with Merlin to hunt down the monster (an afanc). However, when Arthur reports the recovery, Uther believes Gwen to be the sorceress and sentences her to death. When Gwen's father exhibits symptoms, Merlin disregards Gaius's warning by curing him. Uther orders Arthur to search all Camelot for the sorcerer he believes to have caused the epidemic - only a magic trick saves Merlin from having his book found.
The next day, people start dying of a plague which turns their skin white with dark blue veins. The dark sorceress Nimueh casts a spell on a dragon egg which she throws into the castle's water supply. After enigmatic encouragement from the Great Dragon, Merlin decides against giving up and resorts to a magic book Gaius gave him. He prepares for his own match with Valiant, expecting to die. Arthur is furious to be humiliated and fires Merlin. Arthur accuses Valiant of cheating, but the only 'worthy' witness has died and a servant's word is useless against a knight. Sir Valiant has a magic secret weapon: a shield from which the poisonous serpents can come to life and attack. Uther holds an annual tournament for the knights, in which Arthur is the defending champion. Merlin interferes, saving Arthur's life, and is rewarded with a position as Arthur's manservant. At a feast, the disguised mother of the sorcerer casts a spell on the guests and attempts to stab a defenseless Arthur. Merlin disagrees, seeing Arthur as an obnoxious bully. He then discovers the Great Dragon, who tells him that he must protect Arthur until he becomes king and guide him to unite Albion. Merlin realizes he must keep a low profile. A hideous old woman, the condemned man's mother and a sorceress, vows revenge ("A son for a son!") before vanishing. On his arrival, he sees the execution of a man accused of sorcery as the King, Uther Pendragon, has banned sorcery on pain of death. The teenaged warlock Merlin is sent by his mother to lead an anonymous life in Camelot, under the care of the court physician Gaius. But Merlin faces a tough challenge in hiding his dark secret from his best friends. Merlin and Arthur must work together to protect the great kingdom of Camelot against dark sorcery.