'Once Upon a Time' Winter Finale Sneak Peek

The winter finale of OUAT airs Sunday at 8 p.m. ET/PT.

The Dark Ones prepare to obliterate light magic once and for all in this week's episode of Once Upon a Time ("Swan Song"), airing Sunday, December 6 at 8 p.m. ET/PT.

The dark siege of Storybrooke is underway as all of the resurrected Dark Ones target a living soul for sacrifice so that they can return to the realm of the living. With doom imminent, Gold advises Mary Margaret, David and the rest of the heroes to spend their last fleeting moments enjoying the company of their loved ones. Emma, however, refuses to give up, knowing that she is responsible for righting all the poor choices she made as Dark One - there's only one problem, Dark Hook. When they face-off with the fate of Storybrooke at stake, Hook's actions will devastate Emma in a way no one saw coming. In a Fairy Tale Land flashback, the Evil Queen tests Hook's mettle by forcing him to confront a demon from his past before contracting him to dispatch one from hers.

Watch a sneak peek below:

'Once Upon a Time' Sneak Peek: Broken Heart

Sean Maguire, Lana Parrilla and Rebecca Mader. Photo Credit:
ABC/Eike Schroter

The fate of Storybrooke hangs in the balance when Emma and Hook's relationship is tested as never before in this week's episode of Once Upon a Time ("Broken Heart"), airing Sunday, November 29, starting at 8 p.m. ET/PT.

In a Camelot flashback, Hook becomes a Dark One and his lust for revenge against Rumplestiltskin is reignited. When Emma and Hook disagree about their best course of action, the final pieces of the puzzle are revealed as events in Camelot catch up to the present and we witness a charged confrontation between the forces of light and dark that sends our heroes on a collision course with destiny. Meanwhile, in Storybrooke, Hook's centuries old lust for revenge against Gold puts both of their fates in jeopardy while Emma's love faces the ultimate test as she tries to convince Hook to turn away from the darkness before she, Mary Margaret, David and Regina embark on a new mission as an unsuspected evil is released.

Watch a sneak peek below:

'Once Upon a Time' Sneak Peek: Merida Meets Mulan

"You may not need a man to teach you how to fight, but you can
learn a thing or two from me," Mulan tells Merida.

The heroes' Camelot quest culminates with an impossible decision Emma must make in a special two-hour Once Upon a Time event, airing Sunday, November 15, starting at 8 p.m. ET/PT.

The back-to back episodes begin with "Birth," as tensions in Camelot come to a head when Merlin, now under Arthur's control, delivers an ultimatum to Emma: hand over the Dark One dagger and the Promethean spark or he will kill her entire family. Refusing to give in, Emma and our heroes face off against Arthur, Merlin and Zelena in an epic battle of magic and will. Just when the end is in sight, Emma is forced to make a gut-wrenching choice that no one saw coming. Back in Storybrooke, Zelena's pregnancy mysteriously accelerates and Hook goes to new and desperate lengths to get answers from the Dark Swan.

In the second hour, "The Bear King," Zelena and Arthur journey to DunBroch on a mission to retrieve an enchanted relic that will provide the advantage they need to vanquish Emma and our heroes. Their path will cross with Merida's, who is on a journey of her own to pay a debt that her father, King Fergus, owed to the Witch when he died. Merida enlists the help of two friends, Mulan and Ruby, but, in order to satisfy the Witch and save DunBroch, she first must discover the identity of the knight who killed her father. In flashbacks, Merida learns about bravery and honor as she trains for combat and rides alongside Fergus into the infamous battle that claims his life.

Watch a sneak peek below:

'Once Upon a Time' Preview: Can Emma Be Saved?

Hook wants specifics about the plan to save Emma.

Emma and Merlin embark on a perilous quest to retrieve Prometheus' fire from the birthplace of dark magic on this week's new episode of Once Upon a Time ("Nimue"), airing Sunday, November 8 at 8 p.m. ET/PT.

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.

In the sneak peek below, Hook, Mary Margaret, David, Regina and Robin gather to find out how to save Emma from the darkness threatening her soul.

'Once Upon a Time' Preview: Merida Breaks Out of Jail

Paul Telfer (left) as Lord Macintosh on Once Upon a Time.

Days of our Lives alum Paul Telfer (ex-Xander Cook) guest stars as Lord Macintosh on this week's episode of Once Upon a Time ("The Bear and the Bow"), airing Sunday, November 1 at 8 p.m. ET/PT on ABC.

In a Camelot flashback, a chance encounter with Merlin, David, Hook and Belle gives Merida new hope in her quest to save her brothers from the usurping clans of DunBroch. Unwilling to leave anything up to fate, Merida brings Belle along on a dangerous journey that culminates with an invaluable lesson in bravery.

In Storybrooke, Regina, Mary Margaret and David discover the spell that would allow one of Merlin's chosen to communicate with him, but when Arthur fails to reach the missing sorcerer the heroes grow suspicious. Meanwhile, Emma commands Merida to kill Belle in hopes of forcing Mr. Gold's heroic transformation. With Merida unable to disobey Emma's orders, Gold must find the courage to fight for Belle's life or risk losing her forever.

In the sneak peek below, Merlin (Elliott Knight), David (Josh Dallas), Hook (Colin O'Donoghue) and Belle (Emilie de Ravin) sneak into the dungeon at Arthur's castle to free Merida (Amy Manson) and Lancelot (Sinqua Walls).

'Once Upon a Time' Preview: Henry Turns to Dark Swan for Help

Jared Gilmore plays Henry on Once Upon a Time.

Once Upon a Time Season 5 continues with a new episode ("Dreamcatcher") on Sunday, October 25 at 8 p.m. ET/PT on ABC.

In Camelot, as Mary Margaret and David attempt to retrieve the Dark One dagger, Emma uses a dreamcatcher to look into the past to see how Merlin was transformed into a tree. Together, Emma and Regina figure out the critical ingredient they must acquire to free Merlin, but it's a race against Arthur, who does not want Merlin released. Meanwhile, with encouragement from his moms, Henry musters up the courage to ask Violet on a date. Back in Storybrooke, the heroes break into Emma's house hoping to locate Gold, but what they find will give them a glimpse of Emma's end game. Far from prying eyes, Merida sets about the mission Emma has tasked her with and begins molding Gold into the hero they need to draw Excalibur.

In the sneak peek below, when Henry sees his crush Violet's sadness over her missing horse, he turns to the one person he knows can help: Emma.

'Once Upon a Time' Preview: Regina Makes a Promise to Zelena

Regina (Lana Parrilla) allows a muted Zelena (Rebecca Mader) to speak.

Once Upon a Time Season 5 continues with a new episode ("Siege Perilous") on Sunday, October 11 at 8 p.m. ET/PT on ABC.

In Camelot, the heroes feverishly work to free Merlin. Determined to help Emma, David embarks on a quest to retrieve a magical relic that Regina could use to communicate with the imprisoned sorcerer, but, when David leaves, Arthur insists on joining him because the dangers ahead are greater than he can imagine. Meanwhile, Mary Margaret discovers the fate of her old friend Lancelot. 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 as she sets about her plan to draw Excalibur from the stone

In the sneak peek below, Regina (Lana Parrilla) allows a muted Zelena (Rebecca Mader) to speak and confronts her sister about taking away Robin's (Sean Maguire) baby.