Merlin (Elliot Knight) will be reminded of his past as he heads to a heroic quest with Emma aka The Dark Swan (Jennifer Morrison) in the seventh episode of "Once Upon A Time" season 5. The sequel is titled "Nimue" and it will introduce viewers to the childhood romance of the legendary figure in Arthurian legend.

Additionally, a sneak peek video of the episode also features a romantic sequence between Morrison's character and Captain Hook (Colin O'Donoghue). In the clip, the Captain is seen giving a chain to Emma and saying,: "You know I'm a survivor. This ring is why. I've had it for many years, it's the reason I'm alive – or it could be, who knows?"

"Nimue" will even have a surprising twist in the storyline as it shows Wicked Witch Zelena (Rebecca Mader) helping Evil Queen Regina Mills (Lana Parrilla) and others in their mission to steal the Excalibur from King Arthur's (Liam Garrigan) castle, according to Entertainment Weekly.

Teasing about the upcoming sequel, cast member Elliot Knight dished about a heroic quest for Emma and Merlin. "It's really exciting. In terms of what they're doing, all I can say is it's a very personal journey. And I won't say for who. But it's fitting that it's just the two of them, and it's not with everybody else. It's something that's very personal," TV Insider quoted him as saying.

The official synopsis of "Once Upon A Time" season 5 episode 7 read as below:

In Camelot, Merlin spearheads a mission to reunite the dagger with Excalibur so he can use the weapon to save Emma from the darkness threatening her soul. With Zelena in tow, Hook, Mary Margaret, David, Regina and Robin steal into Arthur's castle to take the broken sword from the maniacal king. Meanwhile, Merlin brings Emma along on a journey to confront his ancient nemesis and retrieve the sacred spark he'll need to reforge Excalibur. Both parties are tested, but one suffers a blow that could derail the entire operation. In a flashback to long before the Age of Arthur, young Merlin finds purpose after he is blessed with magic and immortality, but when he falls in love with a young refugee named Nimue, everything changes for Merlin, as their romance starts a chain of events that touches every one of our present day heroes.

While fans of the fairytale series are yet to meet the new fictional character named "Nimue", the Arthurian legend describes her as the true love of Merlin, who was known as "the Lady of the Lake", according to Pop Sugar.

Since the mysterious lady is believed to be someone who trapped the powerful sorcerer in the tree, speculations are rife that she could be the real Dark One. So it remains to be seen how Merlin and Emma over comes her evil powers to reunite the the dagger with Excalibur.

CLICK HERE to watch "Once Upon A Time" season 5 episode 7, titled "Nimue", online on ABC this Sunday, 8 November, at 8pm.

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