The next episode of ABC's Once Upon a Time will be all about freeing Merlin (Elliot Knight).

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ABC has released the plot synopsis for the third episode of Once Upon a Time season 5, titled Siege Perilous. Our heroes are still in Camelot hoping to free Merlin in order to save Emma (Jennifer Morrison) from darkness.

Here is the official plot synopsis:

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"In Camelot, the heroes feverishly work to free Merlin. Determined to help Emma, David [Josh Dallas] embarks on a quest to retrieve a magical relic that Regina [Lana Parrilla] could use to communicate with the imprisoned sorcerer, but, when David leaves, ARTHUR [Liam Garrigan] insists on joining him because the dangers ahead are greater than he can imagine. Meanwhile, Mary Margaret [Ginnifer Goodwin] discovers the fate of her old friend Lancelot [Sinqua Walls]. Back in Storybrooke, ARTHUR seeks David's help to catch a thief who threatens the safety of the citizens of Camelot. Across town, Emma reaches out to a conflicted Hook [Colin O'Donoghue] as she sets about her plan to draw Excalibur from the stone."

We shall see if the previously reported "bromance" between David and Arthur begins to form on this quest for the relic

Guest stars for the episode are as follows:

Lee Arenberg as Leroy/Grumpy, Beverley Elliott as Granny, Liam Garrigan as King Arthur, Joana Metrass as Guinevere, Sinqua Walls as Lancelot, David-Paul Grove as Doc, Gabe Khouth as Sneezy, Faustino Di Bauda as Sleepy, Michael Coleman as Happy, Mig Macario as Bashful, Jeffrey Kaiser as Dopey, and Giacomo Baessato as Grif.

Once Upon a Time airs Sundays at 8 p.m. ET/PT on ABC.