A deadly plague spreads through Camelot. When it seems that sorcery can be the only possible explanation, Merlin and Gaius race to find a cure, while Gwen is arrested and sentenced to death for practising witchcraft.

On a hunting trip, Arthur comes face to face with a creature of great power from the old religion. When Gaius informs them that it can only be killed by magic, Uther refuses to listen and sends out his knights to kill it. Arthur is fatally wounded and Merlin must go to the Isle of the Blessed to save him. But will he be able to pay the price?

New servant Cedric muscles in on Merlin's position as Arthur's right-hand man, and turns the prince against his loyal friend. Merlin is convinced the slippery newcomer is up to something, and he is right - Cedric is a conman and a thief who is after a magnificent jewel, recently unearthed in a tomb far beneath Camelot. Little does he know, his precious prize is more dangerous than he could possibly imagine.

Camelot has never been more vulnerable, but how can Merlin make things right when, thanks to Cedric, he might have lost Arthur's friendship for good? Merlin faces the prospect of turning to the one creature he swore he would never trust again - The Great Dragon.

When Morgana's nightmares spill into waking hours, she becomes terrified that she has the power of magic. Gaius is determined to keep her in the dark for her own good but Merlin won't stand by and watch his friend suffer. He knows exactly what she's going through and he knows she needs the truth. Is Merlin about to reveal his secret at last?

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?

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

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

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?

With Princess Mithian as the perfect bait, Morgana conjures a deception so powerful that the whole of Camelot is taken in - even Merlin himself. But as the storm clouds gather, will the young warlock see through the lies? Or will Morgana at long last fulfil her dreams of revenge?

In the inky depths of an ancient pool, three soothsayers cast a dark judgment upon the King of Camelot.

But despite Merlin’s warnings, headstrong Arthur refuses to take the words of the Disir seriously and their fury rains down on Camelot. Only the greatest sacrifice can appease them, and with the kingdom in jeopardy, is it one that Arthur is prepared to make?

Faced with the King’s uncertainty, Merlin has just one chance to save him from his destiny, but this decision comes at the highest price.

When Gwen is snatched from Camelot without warning, Merlin knows there can be only one person responsible: Morgana. Arthur is determined to rescue his Queen – but it's not going to be easy, for she is locked in the Dark Tower, a place that haunts the dreams of men.

Arthur and his Knights must embark on a quest like no other, battling through a landscape riddled with hidden dangers, perilous obstacles and magical beings. As they near their goal, Merlin's sense of dread reaches breaking point. What twisted game is Morgana playing? And more importantly, just what is the final test that awaits them in the tower?