The relationship between Merlin, and his master, Arthur, has progressively formed and developed over the course of time into a very, very close bond. They, according to divine prophecy, share an interlaced destiny, both being opposites of the same coin. After saving Arthur from getting killed, Uther Pendragon thought he merited something very special and appointed Merlin his manservant. While, though, at first their connection was tarty, they were both very quick to sacrifice themselves for the other (The Poisoned Chalice and The Labyrinth of Gedref). Arthur shows just how deeply he cares for Merlin by frequently teasing and joshing him around and gets great enjoyment by hassling and overloading him with his work, but deep down, cares for him very much. Some have speculated that they shared something more than friendship, and the producers confirmed this in the commentary of the last episode, "Diamond of the Day part two." Julian Murphy called it, "A love story between two men."
- Merlin: "Hey. C'mon, that's enough." -Arthur: "What?" -Merlin: "You've had your fun, my friend." -Arthur: "Do I know you?" -Merlin: "Uh, I'm Merlin. -Arthur: "So I don't know you. -Merlin: "No.." -Arthur: "Yet you called me friend." -Merlin: "That was my mistake." -Arthur: "Yes, I think so."- Merlin and Arthur, The Dragon's Call
- "This merits something quite special. You shall be awarded a position in the royal house. You shall be prince Arthur's manservant."- Uther to Merlin, The Dragon's Call
Merlin and Arthur first meet when Merlin stops him from disparaging and belittling a servant. Arthur starts picking on him and then has some of Camelot's guards toss him in jail, but Gaius is able to have him released, but is consequentially bound and pelted by vegetables by the villagers for defying the prince. Merlin is taking a stroll into the village, but Arthur passes by and goads him into engaging him in a fight with chain-maces. Merlin doesn't stand a chance and quickly resorts to the utilization of his magic, and Merlin having thought to have won, looks away, and Arthur surprises and apprehends him. Some guards grab him but Arthur stops them, saying, "There's something about you, Merlin. I can't quite put my finger on it." Using magic, Mary Collins is able to drown everyone, but Merlin who covers his ears, in the courtroom to sleep with her voice. With everyone asleep, but Merlin, she is about to throw a dagger at Arthur but Merlin using magic dislodges a chandelier, which falls down and crushes her. Everyone awakes, but with the last of her strength, she hurls the dagger at Arthur, but Merlin perceives every second of its movement using magic and pushes Arthur out of the way, saving him. Uther accredits him and names him his son Arthur's manservant, which Arthur has clear aversion and antipathy for.
Knight Valiant uses a magical shield in Camelot's tournament to beat contestants and Merlin informs Arthur of this. Arthur believes him, but when the witness is killed by one of the serpents and thus the evidence nearly expunged, Arthur disemploys Merlin of his position as his manservant for making him look like a fool in front of his father. When it's revealed that Merlin was telling the truth, Arthur admits that he was wrong to have sacked him and reinstates him as his manservant, but eagerly reminds him to clean his chambers, wash his clothes, repair his armor, clean his boots, exercise his dogs, air out his fireplace, change his bed, and muck out his stables.
As Gaius and Merlin are examining a very unnatural cause of death in a person, Arthur calls for Merlin, who answers the door, saying he's sorry he's late, but Arthur sullenly frowns and say he's getting used to it. Merlin shows him the flower Gwen gave him but shows casualness in completely ignoring it and tells Merlin to tell Gaius Uther needs to see him. Merlin asks Gaius why Arthur couldn't have just told him himself, and Gaius explains that it's one of the uses of servants. Arthur, and a group of Camelot's guards, storm into Gaius's chambers, rummaging for any indicative sign of the source of the plague that's befallen Camelot. After searching through the chambers, including Merlin's room, Arthur and the guards shuffle out. To save Gwen, who's been convicted of being a sorceress as a magic poultice was found in her father's house which cured him of an awful plague, Merlin lunges himself at the mercy of Uther and confesses that he's the sorcerer. The guards restrain him, but Arthur is doubtful that Merlin of all people could be a sorcerer and says that he suffers from an illness of severe gravity and that he's just saying this cause he's in love with Gwen, but Merlin is confounded and, staggering in his speech, tries to argue that he isn't, and Uther lets him go but tells him not to waste his time again. Arthur, upon the ward's adjuration, accompanies her and Merlin to destroy the Afanc. The creature swings a punch at Arthur but he ducks. Arthur tries to approach it but, at its massiveness, he backs up. Merlin yells to Arthur to use the lit torch, he sticks it in its face and Merlin using magic causes the fire to lash out and drench the creature, killing it. After the death of the Afvanc and the reversal of the affliction in the town's people, Uther has the guards release Gwen and she's reunited with her father.
The sorceress, Nimueh, seen in the previous episode, poisons a chalice. She screened her identity and masqueraded as a handmaiden using the name 'Cara'. Now 'Cara,' she sneaks into Bayard's quarters and switches the goblet intended for Arthur with her poisoned one. Merlin's fits a red jacket on Arthur from a pile of clothes he sifted through that were used a year ago. Arthur says that because he has to sit through Bayard's speeches, that Merlin should too. Arthur hands the jacket back to Merlin, telling him to remember to polish the buttons. For amusement, Arthur tortures him by making Merlin wear a humorously ridiculous costume. In the courtroom, Bayard is signing a peace treaty between Mercia and Camelot. Merlin feels very vulnerable and embarrassed wearing it and Arthur turns around and grins at him. Bayard hands out ceremonial goblets for King Uther and Arthur, whose is poisoned. 'Cara' pulls Merlin aside and says she saw Bayard tampering with one of the goblets, which Merlin deduces to be poison from what 'Cara' was saying. Merlin runs in shouting that what Arthur's about to drink is poisoned.
- Bradley James says in an interview that his character Arthur's friendship with Merlin is stronger than his love for Gwen.