A year after her disappearance and when almost all hope is lost, Morgana returns to Camelot. While Merlin is afraid she might remember the circumstances of her disappearance and give him away in front of the king, a delighted Uther announces a banquet to celebrate. However, soon afterwards evil magic starts to take hold of the king's mind, putting the safety of Camelot at risk as he is consumed with hallucinations and enemies reach his door. Merlin suspects Morgana is behind the enchantment but his search for the truth puts his life in peril while Arthur is forced to take control and face new foes on his own. Will they succeed to rescue the king and Camelot from destruction?

With the help of the Great Dragon, Merlin manages to return to Camelot only to find out that is it on the verge of invasion: Morgause and Cenred have teamed up and plot against a weakened Uther. Cenred's initial reluctance is won over by the fact that they count on an ally within Camelot walls who will ensure the castle is taken. Uther is unable to rule which forces Arthur to step up front and defend the citadel agains Cenred's powerful army. With the help of Morgause and to make things worse, Morgana plays a deadly card and summons a skeleton army to wreak havoc within the castle walls. Camelot's fate rests once again on Arthur's shoulders and Merlin's magic as they fight in their own way to hold off both an army of the living and an army of the dead. Will they manage to succeed?

When Merlin comes across a secret chamber, he accidentally releases a goblin. The mischievous little creature possesses Gaius, making the wise and renowned court physician turn into a shadow of his former self, quickly developing a taste for gold, ale and magical jokes. To make things worse, the king suddenly becomes bald and a nasty scourge of flatulence hits the royal household. Will Merlin be able to figure out the source of all troubles, return the gobblin back to where he came from and put an end to the havoc before any real damage is done?

Merlin and Arthur find themselves outnumbered in a bar fight but an enigmatic young man helps them win. The man’s name is Gwaine and he risks his own life to protect Arthur but during his act of bravery he is seriously wounded. The Prince decides to take him back to Camelot where he could make a recovery with Gaius' help. Gwaine immediately gets to work: drinking, flirting with the ladies and causing lots of trouble for Merlin who has been instructed to look after him. However, when two unscrupulous knights seem to plot to murder the Prince, will Merlin and Gwaine be able to stop them and save Arthur?

After an unexpected meeting with the enigmatic old sorcerer Taliesin, the wizard takes Merlin to the crystal cave allowing him to witness a glimpse of the future. However, this gesture turns out to be more of a curse than a gift when, much to his horror, Merlin sees Morgana set to kill Uther. The young warlock knows he must do his best to try and stop the future from playing out. But changing the pages of destiny is a very dangerous game and his actions end up having fatal consequences. With the whole of Camelot in a state of grief, will Merlin be able to change the course of destiny and undo the damage he has caused, or will it be too late?

Uther pressures Arthur into an arranged marriage with a visiting princess, Elena, though Merlin soon has reservations after discovering that Elena may not exactly be who she claims to be. As he tries to uncover the princess' dark secret, he learns that Elena's nanny is a Pixie. But what are their motivations? Who do they work for? And most important of all, what benefit do they get from her marriage to Arthur, the heir to the throne of Camelot? Will Merlin be able to get to the bottom of it all and prevent Arthur from making the biggest mistake of his life?

Gwen faces an impossible dilemma when she is forced to choose between saving the life of Elyan, her estranged brother and only sibling or Arthur's, Camelot's prince and the love of her life. When one of them is certain to find death at the hands of Cenred, who will Gwen choose?

Once again, loyalty, love and friendships are tested to the limit as Arthur, Merlin and Gwen are forced to put their minds together to try and find a way out of the cruel quandary. Morgana and Morgause, in turn, will do their best ruin their plans.

Will good conquer evil or will Gwen end up losing someone she loves again?

Arthur embarks alone on a quest to prove himself worthy of the Camelot throne by retrieving the Golden Trident from the Fisher King.

With the Prince beyond the protection of the citadel, Morgana takes the opportunity to use her dark magic. She gives him a precious bracelet that contains a Phoenix Eye, insisting that he wears it at all times for protection. However, the magical jewel takes away Arthur's life force and he is left defenceless in the Fisher King's perilous realm.

With the help of Gwaine, will Merlin be able to reach Arthur in time and fulfil his own quest to protect the future king of Camelot?

An old flame of Gaius' arrives in Camelot under the influence of a Manticore.

When Uther banishes Gwen from the kingdom, Arthur resolves to leave Camelot with her.

Camelot's legendary tournament only has one rule: there are no rules whatsoever. Terrifying warriors start to fill the mythical city, Gilli between them. Despite his small stature, Gilli is ready to join the action and committed to achieve victory with a secret weapon to help him: magic. When Gilli begins to realise the full extent of his powers, Merlin becomes torn since his new friend is putting his own life in danger as well as threatening the very heart of Camelot with his actions. Will Merlin be able to make Gilli see sense before it's too late?

Arthur and Merlin embark on a dangerous mission to capture the Cup of Life, a powerful magical artifact that carries the gift of immortality. However, before they are able to retrieve the Cup they fall prey to Jarl, an unscrupulous slave trader. They manage to escape when a trusted friend comes to their rescue but with Jarl's help, the Cup of Life ends up in Morgause's hands. Now that the dreadful sisters count on an immortal army at their disposal, will Morgause and Morgana overthrow Uther once and for all?

Will Arthur be able to save Camelot from the evil Morgana? Morgana, newly crowned as Queen of Camelot, begins a reign of terrible evil over the innocent citizens of the kingdom. Counting on Morgause and her immortal army at her command all hope seems lost for Uther, who is forced to witness how his kingdom crumble under the unimaginable cruelty of his own daughter. Meanwhile, on the outskirts of Camelot, Arthur recovers his strength and plans a counter attack with the help of a few loyals at his side: Gwaine, Lancelot, Elyan and Percival. However, Merlin is aware that not even a skilful warrior like Arthur can defeat an immortal foe without magic. Will he be able to reclaim the great sword Excalibur from the Lake of Avalon in time to save the lives of those he cares the most about?

Evil sorceress Morgana summons mighty gatekeeper the Cailleach, who opens a door to another world from which hellish creatures pour forth. As Arthur and his loyal knights take up arms, Merlin discovers the only thing that will stop them is an unimaginable sacrifice.

The kingdom is on the brink of collapse and Morgana poised to strike, in the final part of this opening episode of the fantasy drama. 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's the power of love that changes all their lives for ever.

The mighty citadel is buzzing in anticipation of the Prince's birthday celebrations, as the fantasy drama continues. But Arthur's old adversary, Odin, promises to ensure this is one party Camelot will never forget - for among the assembling guests lurks a deadly assassin set to strike.

As the dust settles, Camelot is left devastated. Just how far is Merlin prepared to go to put things right; would he really risk everything and reveal his secret?

A mysterious visitor arrives in Camelot seeking a very special prize: a dragon's 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.

Merlin becomes a deadly weapon in Morgana's fight for supremacy when he falls into her hands. By recurring to ancient magic, she manages to turn friend against friend and creates the perfect assassin out of the young sorcerer which puts an oblivious King Arthur in great danger. Will anyone notice Merlin's unusual behaviour before he is able to do any serious harm to the King?

Morgana joins forces with enigmatic wizard Alator to uncover a secret that could change the course of destiny, as the magical drama continues. With allies on both sides of the castle walls, can anyone stop her before Merlin's greatest secret is revealed?

A mysterious illness draws Merlin to a distant village. But it soon becomes clear that there is more at stake than just his patients' well-being as something sinister turns the air sour. Far from home and with no-one to trust, Merlin becomes embroiled in a deadly game of cat and mouse. No longer sure who is the hunter and who is the hunted, can the young warlock survive long enough to uncover the truth?

When Sir Lancelot returns from the dead, old feelings reignite, as the drama continues. Gwen must fight temptation before she commits an unspeakable act of betrayal; one that would destroy the legacy of Camelot forever.

With heads and hearts thrown into turmoil, Merlin becomes suspicious. Can a man really defy death, or is there something more sinister at play?

The Camelot Knights stumble across an eerie shrine deep in the forest, its chilling atmosphere betraying a dark history best left undisturbed, as the magical drama continues.

But when Elyan ignores Merlin's warning, his actions spark a chain of events more frightening than anyone could possibly have imagined... Can a grievous wrong be put right? Or will past demons change the future forever?

Morgana ends up discovering a powerful ally in the Southron warlord Helios and they come up with the perfect plan to bring Camelot to its knees. With Arthur preoccupied by the beautiful Princess Mithian, it ends up falling to an absent friend to raise the alarm.

Morgana is now the head of a vast Southron army and a deadly net is closing around Camelot. After the sorceress strikes everyone is forced to run for their lives including Arthur. It is down to Merlin to try and save Arthur from Morgana's clutches.

Morgana and Helios have successfully captured Camelot, and Merlin and Arthur are outlaws on the run, in the last episode in this season of Merlin. Trapped in Ealdor with a ruthless army closing in, their situation becomes desperate. Arthur must take control before Camelot is lost forever… But faced with Agravaine’s betrayal and the strength of Morgana’s force, the young King has lost his conviction. Only Merlin can restore his faith, and only an extraordinary act can prove to the King that he was born to rule. Will the young warlock convince Arthur before his dreams of Albion fall to pieces?