Once Upon a Time, Season 5

Immediately after becoming the Dark One, Emma disappears and the heroes must band together to save her, but first they have to find her, which will require the help of an unlikely ally.

In an effort to protect Emma, Regina steps up in a surprising way that will test her mettle as a force for good. King Arthur and Queen Guinevere throw a royal ball to welcome the heroes to Camelot, but when the celebration takes a deadly turn, David and Robin must leap into action or lose a crucial asset in the fight to save Emma. Back in Storybrooke, Hook deploys a tried-and-true technique in hopes of bringing Emma back to the light while the heroes discover that some unexpected baggage has followed them home from Camelot

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. Back in Storybrooke, Arthur seeks David’s help to catch a thief who threatens the safety of the citizens of Camelot.

After receiving a cryptic warning from Lancelot about Arthur's intentions, Mary Margaret realizes Arthur may be the heroes' biggest threat, but when she is unable to convince David of the danger, she takes matters into her own hands. Meanwhile, Hook's unwavering love for Emma provides a glimmer of hope in her struggle against the unrelenting voice of Rumplestiltskin.

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.

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.

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.

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.

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 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, resulting in a charged confrontation between the forces of light and dark.

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.

Emma, Regina, Mary Margaret, David, Robin, Henry and Gold arrive in the underworld, on a mission to rescue Hook. Meanwhile, in an Enchanted Forest flashback, a familiar face from the Evil Queen's past returns to present Regina with the perfect birthday gift.

An escapee from Hades' prison informs the heroes that Hook is being held captive, but to rescue Hook they must face a terrifying beast that guards the prison. Mary Margaret searches for an old childhood friend who knows how to defeat the monster.

Hades threatens to condemn Hook to the River of Lost Souls after Hook refuses to choose which three of his friends will have to remain in the Underworld. Meanwhile, Gold is eager to help Emma, Snow, David, Regina, Robin, and Henry find Hook so he can return home to Belle, but in order to do so he must find his ex-wife Milah in the Underworld, and receive her help.

Hook and Emma must defeat Hades in order to return to Storybrooke with Snow, David, Regina, Robin, Henry, and Gold. A surprise visit from Hook's departed brother Liam just might provide the lead they were looking for. Meanwhile, Hades redoubles his efforts to trap the heroes in the Underworld by playing them against one another.

The Heroes continue searching for a way to free everyone from the Underworld. At the mercy of Hades, Gold creates a portal to Storybrooke, which transports Belle, Zelena, and Baby Hood to the Underworld. Belle is reunited with Rumple only to learn shocking news that will change her life forever. Meanwhile, Snow and David hopelessly attempt to send a message from the Underworld to their son.

Belle turns to Rumplestiltskin to find a way to protect their child from Hades. Meanwhile, Hades meets with Gaston in the Underworld and encourages him to seek revenge on Rumplestiltskin. As the heroes try to find a way to defeat Hades, Emma has a terrifying nightmare that she realizes is coming true.

In flashbacks, Ruby and Mulan find themselves in Oz, where they meet Dorothy. After the three witness Zelena's return to Oz, they look for a way to defeat her once and for all. However, Dorothy mysteriously disappears, and Ruby's search for her new friend lands her in the Underworld.

Hades wants a future with Zelena outside of the Underworld. Regina overhears this and enlists Cora's help to find a way to separate Zelena from Hades. However, Cora reveals a family secret that could change Regina and Zelena's lives forever.

Hades turns to the heroes to ask for help with getting Zelena back from Rumplestiltskin and Peter Pan. In return, he offers to take all their names off their tombstones. However, when Hook is still unable to leave, he and Emma must journey into the depths of the Underworld.

Emma, David, Regina, Robin and Henry return to Storybrooke and reunite with Snow, but still have to contend with Hades, who continues to deceive Zelena as he lays out his plan to use the Olympian Crystal to take over the town.

Regina reels from the death of Robin Hood. When the heroes discover Gold has stolen Hades' Olympian Crystal and tethered all of Storybrooke's magic to it, they set out to stop him. Henry decides he no longer can stand all the pain magic has caused his family, so he goes rogue, with Violet in tow. Meanwhile, Zelena, Snow, David, and Hook attempt to open a portal that will return Merida and the other Storybrooke guests to their homes.

With the possibility of magic being destroyed and the fate of Storybrooke hanging in the balance, Emma and Regina race to track down Henry before Gold can find him. Regina continues to struggle with her frustrations over her former evil self and, elsewhere, Snow, David, Hook, and Zelena are imprisoned.

Bonus "Birth" episode with special audio commentary from Cast Member Colin O'Donohue, Executive Producer/Writer David H. Goodman and Producer/Writer Jerome Schwartz. 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.