Treasure is found in an ancient tomb under Camelot. Gaius is worried that the treasure belongs to Cornelius Sigan, an evil sorcerer and wants the King to have the tomb resealed. A new servant called Cedric attempts to turn Arthur against Merlin. Merlin finds out that Cedric is up to and finds himself being forced to turn to The Great Dragon.
Arthur is determined to win an upcoming jousting competition at Camelot. Gwen challenges Arthur to give up his spoilt ways after he goes undercover with her and Merlin. Myror shows up at Camelot determined to hug Arthur. Arthur is determined to prove himself and win the contest unaware that he is in danger.
Morgana is worried she has magical powers when he nightmares start to become a reality. Merlin is determined to help her even though Gaius is against the idea. Morgana finds herself being reunited with the strange young druid boy Mordred who the Dragon has predicted will be person who ends up killing Arthur in the future.
After Gwen is mistaken for Morgana she is kidnapped by Hengist. Arthur attempts to rescue her and Merlin thinks that Arthur cares about her. Arthur discovers Lancelot has already shown up when he tries to rescue her.
Merlin and Gaius suspect that Lady Carina is not quite as she seems after showing up in Camelot. Arthur isn't happy when his father flirts with her. When Merlin discovers that she is really a troll he finds it impossible to get Arthur to listen to him. Merlin tries to stop Catrina from ruining Uther's life but she has her eyes set on an even bigger prize.
Queen Catrina settles into her new role at Camelot and her influence over Uther increases. Merlin is forced to go Merlin tries to expose Catrina without being caught and break her hold over the kingdom.
Uther is determined to once and for get rid of all the magic being performed inside Camelot. Aredian, a witch finder is called to Camelot to help deal with the problem. Gaius tries to make Merlin see how much danger he is in. Morgana is certain that Aredian will discover her secret and Merlin attempts to protect bother her and Gaius.
Arthur is challenged to a dual by a mysterious warrior. Arthur and Merlin then find themselves on a quest on Morgause's behalf. A dark secret is discovered by Arthur that could change Camelot forever.
Freya is found by Merlin trapped in a bounty hunter's cage and decides to try and help her escape. Merlin refuses to listen to Gaius' warnings not to get involved. After freeing her Merlin hides Freya in the tunnels beneath Camelot. Merlin is forced to make some hard decisions to keep Freya safe.
Peace talks are held at Camelot when dignitaries from rival kingdoms arrive. King Alined is determined there will be no peace though and will use magic to make sure his wishes happen.
Alvarr is determined to allow magic to be used gain and destroy Camelot. Alvarr needs to reclaim the Crystal of Neahtid to make his plan work. Alvarr and Morgana try to get their hands on the crystal and use a druid boy to help them. Merlin is surprised when he finds out the real power of the crystal.
For the first time in over 300 the fires of Idirsholas burn years and Gaius is worried that a sorcerer has revived the deadly Knights of Medhir. Morgause returns and is determined to end Uther's reign at Camelot.
The Great Dragon has been set free and fully enraged turns his unhappy hatred towards Camelot without pity. The castle is crumbling down and Arthur and his men realize they won't be able to hold out for much longer. The only wait to defeat the Dragon appears to be a Dragonlord, but Uther wiped them all out of the kingdom years ago. However, Gaius admits that there might be one of them alive and hiding. The last Dragonlord becomes not only the only hope of future for Camelot but also a key to Merlin's own past. Will Arthur and Merlin manage to find Balinor in time to save the kingdom and persuade him to return to Camelot to save his enemy, Uther?