Merlin is stunned when his mother, Hunith, turns up in Camelot, bruised, battered and desperate for help. Their village has been attacked by a bandit, who is demanding all of the harvest. But if they give Kanan their food, they'll starve to death.
Merlin gets Hunith an audience with the King. Uther listens to her story but refuses to do anything. Ealdor is beyond the boundary of Camelot's realm, none of Uther's soldiers can cross the border and to do so would be an act of war. Hunith makes an emotional plea that we can see affects the assembled court, but Uther won't be swayed.
Merlin tells Arthur that he can no longer be his servant. He has to protect his mother and friends - he'll be leaving in the morning. Arthur wishes Merlin luck and thanks him for being a loyal servant.
Merlin goes to Gwen to pick up some weapons and armour but when he gets there he finds Morgana with Gwen. After hearing Hunith's appeal, they couldn't let Merlin go alone. Merlin tries to argue, but they're both determined to help the villagers.
The gang make camp for the night in the woods. As Merlin lies unable to sleep - he hears the sound of a horse approaching through the darkness. Fearing trouble, he readies his sword but it's not bandits, it's Arthur - he tells Merlin that he couldn't let him go alone.
The following day, the company rides to Ealdor. When they arrive, they find Kanan and some of his men ransacking the place. Kanan is forced to back down as Arthur shows his sword prowess, but he vows to return and, when he does, the whole village will pay with their lives.
Arthur gathers the villagers and convinces them that they have to fight, but an old friend of Merlin's (William) refuses. Arthur refuses to be rattled by him and the rest of the village agree to fight.
Merlin speaks to William and tries to convince him to be more positive, but he won't listen, and accuses Merlin of forgetting where he came from. Merlin counters that Arthur is his friend. William laughs at this and asks if Arthur therefore knows about Merlin's magic - only he thought it was banned in Camelot. William's words ring in Merlin's ears. Is he just Arthur's servant after all? William tries to goad Merlin into using his magic to help the village. Merlin refuses to be drawn, but we can see William's words get to him.
That night, Arthur gathers the men in a circle to forge their battle plan but he's interrupted as Gwen leads the women of the village forward and announces that they're ready to fight, too. Arthur smiles at the heart shown by Gwen but she won't be put off. They have as much right to fight for their lives as the men do and if the battle is lost they'll be killed anyway - Arthur relents and starts to lay out his plan.
Meanwhile, Merlin tells his mother he knows the villagers stand little chance of success. He will have to use magic if they are to win - if Arthur sees him, then so be it...
The following morning, Merlin goes to put on Arthur's armour for him, but the young prince refuses his assistance. Merlin's got his own to put on - the two men suit up, as equal as we're ever likely to see them. They wish each other luck and shake hands - they both know that this could be the end of them but Merlin tells Arthur it won't be.
We hear the roar of Kanan's men. They appear over the crest of a hill charging towards the village . An epic battle ensues. Though the villagers fight valiantly, Kanan and his men are too strong and too many - they slay all in their path.
Help comes from an unexpected quarter for Merlin during the fighting when William joins in the battle. However, despite the extra manpower, the villagers are losing badly. In desperation, Merlin summons a whirlwind to help flatten Kanan's men. With the odds stacked slightly more in their favour, the villagers start to win. Arthur takes advantage and fights Kanan in mortal combat. It looks like Kanan's been killed but, with his last breath he goes to attack Arthur. William manages to save Arthur but is injured in the process.
As they tend to his wounds, Arthur wants to know where the winds suddenly came from. It looks like Merlin's about to confess when William steps in - it was him. Arthur says that no-one should ever know he has magic and leaves.
A pained William tells Merlin he understands why he has to keep his magic secret and that it is the right thing to do - Arthur will make a great king with Merlin's help. His wounds are severe and after an emotional goodbye he dies in his friend Merlin's arms.
They put William to rest - Merlin wants to stay with his mother but Hunith won't have any of it. She's seen the type of man he's becoming and doesn't want to get in the way of it. She believes that in time, Arthur will know Merlin's secret, but until then, it must remain just that - a secret.
The villagers wave farewell as Merlin, Arthur, Morgana and Gwen ride off into an improbably bright and perfect sunset - with Arthur reeling off a list of duties Merlin will have to catch up on when they return to Camelot.
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