Morgana takes the dying Morgause to the Isle of the Blessed where she unwittingly tears the veil to the spirit world, unleashing the Dorocha, invisible ghosts that begin to attack the kingdom. At Camelot, where a weakened Pendragon has given over much of his rule to his scheming brother Agravaine, Merlin senses what is happening but finds his magic inadequate to stop it. As Camelot fills with refugees Gaius reasons that, as one death opened the portal, only another will close it. Arthur offers himself as the sacrifice and travels to the Isle of the Blessed with Merlin...
The kingdom is on the brink of collapse, with Morgana poised to strike. As Lancelot races back to Camelot with the dying Merlin, Arthur must continue on his mission to vanquish the Dorocha without them. Though the Knights know their journey to the Isle of the Blessed is fraught with danger, none could anticipate the sacrifice Arthur intends to make there. Friendship and loyalty are tested to the limit, but in the end, it is the power of love that changes all their lives forever.
The mighty citadel is buzzing in anticipation of the prince's birthday celebrations. But Arthur's old adversary, Odin, promises to ensure this is one party Camelot will never forget. For amongst the assembling guests lurks a deadly assassin, set to strike. As the dust settles, Camelot is left devastated. But just how far is Merlin prepared to go to put things right? Would he really risk everything and reveal his secret?
The mysterious Julius Borden arrives in Camelot with news of a magical secret that threatens to change the landscape of the kingdom forever. He has located the final part of the key to the tomb of Ashkanar, an ancient mausoleum which holds a very special treasure: the last remaining dragon's egg. Merlin is understandably drawn in by Borden's news, and promises to help him. But just who is the enigmatic stranger and, more importantly, what does he really want with the egg?
Arthur faces his first true test as King when he incurs the wrath of the formidable Queen Annis. With the lives of thousands hanging in the balance, Arthur must find the strength to be his own man and become the leader Camelot so desperately needs.
When Merlin falls into Morgana's hands, he becomes a deadly weapon in her fight for supremacy. Using ancient magic, she pits friend against friend to create the perfect assassin. An oblivious Arthur is in great danger. Will anyone notice Merlin's unusual behaviour before he does the king some serious harm?
When the menfolk of Guinevere's home village fall victim to a mysterious illness Gaius sends Merlin, along with Guinevere and the knights, to cure them but they are side-tracked by a waif-like girl, Lamia. Only Merlin and Guinevere suspect, rightly, that she is a witch and soon the knights fall under her spell, succumbing to the same sickness. Arthur rides out with Gaius, who has realized the girl's secret, but will they rescue Merlin and Guinevere or can Merlin defeat Lamia without revealing his magic powers?
Learning from Agravaine that Arthur plans to wed Guinevere Morgana uses necromancy to revive Lancelot though he has no proper recollection of his past life and, grateful to Morgana, returns to Camelot to seduce the future queen. Guinevere resists, until she is presented with an enchanted bracelet supplied by Morgana for Lancelot to give her. The two meet in secret and are observed by Arthur. Merlin, suspicious of events, convinces Gaius of how the knight was resurrected but can they stop Arthur from banishing Guinevere and Lancelot from being put to death?
The knights come across a shrine built on a site where druids were massacred and a thirsty Elyan inadvertently desecrates it by drinking from its well. As a result he is possessed by a spectral boy, who tells him his ghost can only rest if the perpetrator of the massacre is slain and bewitches him into trying to kill Arthur, the son of Pendragon, who murdered druids. After a bungled effort Elyan is pursued by Merlin and Arthur back to the shrine where a surprise revelation leads to some hope for the restoration of the old ways.
As Arthur celebrates his engagement to Princess Mithian to unite their countries the banished Guinevere witnesses a raid on her village by war-lord Helios and afterwards overhears him plotting with Morgana to invade Camelot. They will enter the stronghold through the siege tunnels, plans of which have been given them by Agravaine. She escapes to inform Merlin but refuses to see Arthur, who inevitably disbelieves his uncle's treachery when told of the plot. However he still has feelings for Guinevere and calls off his engagement to Mithian.
As Morgana's forces capture Camelot,Arthur at last comes to see his uncle's treachery. He is reluctant to flee but Arthur bewitches him into escaping with him, making him temporarily lose his memory and dressing him as a peasant. Elyan, Gaius, and Gwaine are taken prisoner though Morgana is impressed by Gwaine's performance in a trial by combat. Separated from Leon and Percival Merlin and Arthur fall in with a pair of smugglers, Tristan and Isolde, after which Merlin restores the young king's memory to reveal his identity to the couple. The quartet escape to Ealdor, ...
Merlin summons the dragon to vanquish the pursuers and uses his magic to kill Agravaine. Hiding in the woods with Guinevere, Tristan, and Isolde, Arthur confesses his self-doubt to Merlin and feels he has failed his subjects. But Merlin proves to him that he is worthy to be king by getting him to extract the legendary sword from its stone. In front of Leon and Percival and many other fugitives from the court Arthur accomplishes the feat, inspiring them to claim back Camelot by entering through the same siege tunnels and freeing the prisoners. Finally Camelot will be ...