The third series of BBC’s Merlin begins on Saturday 11 September at 7.25pm on BBC1. The series kicks off with The Tears of Uther Pendragon and it’s a two-part story. Check out the official synopses for Part One and two below (spoilers).

301. The Tears of Uther Pendragon – Part One

It has been a year since Lady Morgana disappeared and no trace of her has been found, as the fantasy drama starring Colin Morgan, Bradley James, Anthony Head and Richard Wilson returns for a new series.

Just as it seems all hope is lost, Merlin and Arthur pick up a trail. Set upon by bandits it seems they may perish but Merlin’s secret magic saves the day. As the dust settles, a mysterious, bruised and bloodied figure approaches the group: it’s Lady Morgana.

Camelot rejoices at her return but Merlin is worried that Morgana will remember the circumstances of their last meeting and tell King Uther that he tried to kill her. The King will not understand that he did it to save Camelot from Morgana’s half-sister, sorceress Morgause’s deadly enchantment; Merlin would be executed on the spot.

Morgana promises Merlin that she has learnt the error of her ways and repents for the evil things she has done. Morgause no longer has any hold over her and Morgana forgives Merlin and promises to keep his secret.

Uther and Morgana enjoy a tearful reunion. The King is delighted that his ward has returned and immediately announces a banquet in her honour. But is there more to her return than meets the eye?

As the evil magic begins to take hold of Uther’s mind, Gaius urges Arthur to take command and Merlin begins to suspect that Morgana’s repentance is not all it seems. Can Merlin find out what is really going on before Camelot is cast into the greatest peril it has ever known?

Katie McGrath plays Morgana, Colin Morgan plays Merlin, Bradley James plays Arthur, Anthony Head plays Uther, Emilia Fox plays Morgause, Tom Ellis plays Cenred, Richard Wilson plays Gaius and John Hurt is the voice of the Dragon.

302. The Tears of Uther Pendragon – Part Two (airing Saturday 18 September)

The young warlock struggles to recover from the serket’s poison, as the fantasy drama continues. Meanwhile, Morgana and Morgause are free to step up their plans for the invasion of Camelot.

Morgause continues her manipulation of Cenred, as he prepares to launch an attack on the citadel, but Cenred knows he cannot take the castle alone. Morgause promises him that they have an ally within King Uther’s court who will ensure they win the day – no one can fight a battle on two fronts. Morgause gives Morgana a powerfully enchanted rowan staff to aid her in her magical treachery.

King Uther is still unable to rule as he recovers from the enchantment inflicted by the mandrake root. So, as Cenred’s army attacks the citadel, Camelot’s fate now rests on Arthur’s shoulders. The young prince and his men fight bravely but, just as they think the tide might turn, Morgana plays her deadly card. In the vaults beneath Camelot she uses the rowan staff to summon a skeleton army to wreak havoc within the castle walls.

Arthur and his men cannot hold off both an army of the living and an army of the dead. Merlin knows that their only hope is for him to stop Morgana and vanquish the enemy within. Will he be able to do so without revealing his own magical powers?

Merlin is played by Colin Morgan, Morgana by Katie McGrath, Morgause by Emilia Fox, Cenred by Tom Ellis, King Uther by Anthony Head, Gaius by Richard Wilson and Arthur by Bradley James. The Dragon is voiced by John Hurt.