Merlin, a young warlock born with the gift of magic, enters the city of Camelot, a wonder of activity and sights for the country boy. However, that wonder is soon replaced by trepidation when he happens upon the public execution of Thomas James Collins. The condemned's crime -- using enchantments and magic. King Uther Pendragon warns the citizens of Camelot -- let this be a lesson that you will suffer the same fate if you practice magic, as he himself has banned sorcery. The drums beat, and at Uther's signal, Thomas Collins is beheaded by axe.
After the beheading, King Uther calls for a festival to celebrate 20 years since the Great Dragon was captured and Camelot was freed from the evils of sorcery. Mary Collins wails in grief and calls Uther the only evil in this land, with his hatred and ignorance, for killing her son. She promises him that before this celebration is over that he will share her tears. When she threatens the life of Arthur, his son, Uther orders her seized. However, she produces a spell and vanishes in a cloud of smoke.
After that jarring introduction to Camelot, Merlin meets his new employer Gaius, the court physician. When Merlin accidentally startles the old Gaius into a fall over the railing, he uses magic to save his life. Gaius asks Merlin what he just did, but he denies having any magical powers. Gaius asks him where he learned it and presses until Merlin admits to being born like this. Gaius doesn't believe him, but promises not to tell the king of his suspicions that Merlin used magic. And, thanks him for saving his life. Later, Gaius reads a letter from Merlin's mother, asking him to protect her son and nurture his gifts.
Uther finds Morgana, his ward, and asks her why she isn't joining the feast. She doesn't feel like celebrating someone getting his head chopped off. She chastises him for his extreme action and sympathizes with his grieving mother. Uther says if she'd been here 20 years ago she'd think differently. When Morgana asks how long he's going to punish people for what happened then, he says until magic is eradicated from his kingdom. He tells her that she must attend Lady Helen's performance, to show respect for their finest singer. Morgana warns him that the more brutal he is, the more enemies he'll create.
Lady Helen, a famous singer en route to Camelot to perform at the festival, is sitting in her tent at camp when Mary Collins enters. She stabs an effigy, killing Lady Helen, and then uses sorcery to assume her appearance. However, though Mary Collins appears to be Lady Helen, she must avoid mirrors, as any reflection will reveal her true form.
Merlin is awakened by a voice calling his name. At breakfast, Gaius tests Merlin by purposely knocking a bucket of water off the table. Merlin involuntarily stops it mid-air. Now, he can't deny that he knows magic. Gaius wants to know how his young assistant stopped the bucket, if he incanted a spell in his mind, but Merlin has no idea. "It just happened." Gaius sends him on errands, warning him that magic will get him killed.
Merlin sees a young knight, whom he doesn't know is Arthur, impressing his friends by making his servant Gregory run with a wooden target as he throws knives at it. From a window, Guinevere watches, concerned. When Merlin sees the bullying, he tells the arrogant noble, "That's enough." Not used to being challenged, Arthur dares him to take a swing at him. Merlin does, and in a swift defensive move, Arthur pins Merlin's arm behind his back. Merlin learns he just threw a punch at the king's son, and is taken into custody and thrown into a cell.
Mary Collins, as Lady Helen, arrives at the castle. A puddle of water reveals her true reflection, but she's the only one who sees it. She greets King Uther; her guise goes off without a hitch.
In the morning, Merlin is once again awakened by the mysterious voice. An angry Gaius arranges Merlin's release. As punishment, Merlin is placed in the stocks where kids gleefully pelt him with rotten produce. Guinevere, Morgana's lady in waiting, approaches and calls him brave.
After the pelting, Gaius asks Merlin what his mother said about his gift. Merlin says his mother said he was special, to which Gaius agrees. Gaius has never come across someone who uses magic just by will of mind. Usually, they have to study and learn incantations to produce spells. When Merlin asks Gaius if he ever studied magic, he says that Uther outlawed magic because it was being used for evil, and that included slaying all the dragons except for one, that he kept as an example. That dragon is imprisoned deep beneath the castle dungeon where no one can free it.
Gaius sends Merlin to deliver some potion for Lady Helen's voice. When Merlin enters her room, she's not there, but he sees the effigy and a book of enchantments. Curious, he tries to sneak a peek at the book, but "Lady Helen" enters and wants to know what he's doing there. Merlin hands her the potion, not seeing "Lady Helen's" true reflection in a mirror. Mary Collins, who did see the reflection, watches Merlin suspiciously as he leaves.
In town, Merlin passes Arthur, who insults him. Merlin insults him back, even calling him a "prat." Arthur challenges him to a fight using flails. Merlin, against his better judgment, accepts. Though Merlin's clearly outmatched in traditional fighting, he covertly uses magic to disarm Arthur and knock him on his royal prattish behind. However, when Merlin becomes distracted by Gaius watching the fight, Arthur clobbers him with a broom. Arthur, who could send Merlin to his death for the affront, decides to spare him. There's something different about Merlin that he can't put his finger on. And, the prince adds, though he may be an idiot, he's a brave one.
Gaius, after yelling at Merlin for his stupidity, tends to his wounds. Merlin wonders why he was given magical gifts. Gaius says maybe that's a question for someone with more wisdom than himself. Meanwhile, Mary Collins/Lady Helen has dinner with King Uther. He asks her to sing but she declines, saying that she's saving her voice for tomorrow. She mentions that is must have been hard for Arthur to grow up without a mother, pointedly saying that the bond between mother and son is hard to replace. She says she's looking forward to her performance the following day.
At night, the same voice wakes Merlin. This time, he sneaks past two guards and follows the voice down deep into to a cave beneath the castle. The Great Dragon, kept prisoner by a long chain, flies to a perch. He marvels at how small Merlin is, for a man with such a great destiny. The dragon tells Merlin that Arthur will unite Albion, and that he was given his magical gift for a reason -- to protect Arthur. Merlin doesn't want to accept this, but the dragon says it's his destiny. When Merlin says that the Arthur he knows is an idiot, the dragon laughs, saying perhaps his destiny is to change that.
The next morning, Gaius asks him to deliver medicine to Morgana, who is suffering from nightmares. Merlin arrives in her quarters, only to find the beauty in the middle of trying on dresses. Not seeing who entered, she mistakes the presence in her room for Gwen, who arrives just in time to stop Morgana from noticing she's been talking to a man. After sharing a silent laugh at the situation, Merlin thanks her and runs out of the room.
A servant delivers a basket of fruit to Mary Collins/Lady Helen, compliments of King Uther. The servant is thrilled to be in the presence of the great singer and talks to her about her own aspirations as she tidies her room. She takes the cover off the mirror and looks in horror when she sees the hag-like face of Mary Collins in the mirror. Mary grabs the terrified woman by the wrist and drains the life out of her.
In the banquet hall, Merlin and Gaius arrive as Arthur and friends mingle. Morgana enters, her beauty captivating every male set of eyes present. Gaius sees and reminds Merlin they're here to work. Gwen makes an awkward attempt to talk to Merlin just before Uther introduces "Helen," who sings a song that puts everyone except for Merlin under a sleeping spell. As she sings, the room darkens and cobwebs grow over the guests and room.
Unaware that Merlin is still awake, "Helen" unsheathes a dagger and prepares to stab Arthur. Using magic, Merlin severs the chain suspending the chandelier and it drops onto Helen, crushing her. The spell fades, and everyone awakes. The veneer of Lady Helen gone, Mary Collins is exposed. Using her last bit of strength, she hurls the dagger at Arthur. Merlin intervenes once more, slowing time so he can push Arthur to safety. Mary Collins dies, and Arthur is shocked his nemesis saved his life. Uther, grateful for Merlin's heroic actions, appoints him as Arthur's manservant. Both Merlin and Arthur fail to see anything good about this.
Gaius calls Merlin a hero, both for saving his life and Arthur's, adding that it appears a purpose has been found for his magic. Though Merlin isn't pleased with the thought of being Arthur's manservant, he accepts his destiny. Gaius gives Merlin a book of magic to read in secret. Thrilled, he promises to "study every word." A royal messenger knocks on the door and says that Prince Arthur wants him right away. "Your destiny is calling," Gaius says.