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. Meanwhile, in the Enchanted Forest, Emma struggles to resist her dark urges as she searches for Merlin in the hope that he can stop her transformation. Along the way to Camelot, she gets help from the plucky and brave warrior princess Merida, as well as King Arthur and his Knights of the Round Table. Written by tanayanaya

While Prince Arthur organizes a ball in Camelot, darkness rises in Storybrooke, to the search of a savior.

A royal ball is held in Camelot, but a dark turn of events forces David and Robin to take action. Meanwhile, Regina's fortitude is tested as she tries to safeguard Emma; and back in Storybrooke, Hook attempts to bring Emma back to the light.

In Rumplestiltskin return, Emma takes her chance at the taking of Excalibur, while King Arthur's real identity is revealed.

Emma and Regina devise a plan to free Merlin, but they lack a pivotal ingredient. Meanwhile, Mary Margaret and David seek an important dagger; Henry asks Violet to go on a date; and Merida attempts to carry out a covert mission Emma has assigned her. Written by Stanny

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 town, 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. Written by NikolaLevic97

Zelena and King 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. Written by ABC

Red and Mulan return to help Merida uncover the truth about her father's death.

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.

Emma, Regina, Mary Margaret, David, Henry, and Gold arrive in the underworld, arrive on a mission to rescue Hook, only to discover that their search will be more difficult than they had anticipated. The inhabitants of the underworld are all souls with unfinished business and many with quite personal vendettas hound our heroes at every turn. Meanwhile, in an enchanted forest flashback, a familiar face from the Evil Queen's past returns to present Regina with the perfect gift.

In the Underworld, an escapee from Hades' prison informs the heroes that Hook is being held captive. But before the heroes can 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. However, once reunited, she discovers that her friend is no longer the hero he once was. Meanwhile, in an Enchanted Forest flashback, a young Snow White struggles to preserve peace in her kingdom and must learn how to be a true hero if she wants to one day become queen.

Gold wants to get back to the real world and Belle so he agrees to help Emma get to Hook with the aid of his ex-wife, Hook's former lover, Mila. While they are on their way to save Hook, Hades is torturing him slowly while lowering him into the River of Lost Souls. Regina works with Cruella to master her magic in the twisted world of Underbrook. She is in search of Daniel's grave with the hope that he is not trapped there as well. Gold and Mila stay with the boat while Emma rushes to save Hook. Hades appears and proposes a deal with Gold to leave everyone behind while he goes back to the real world. Gold stays true to form and accepts the deal and thrusts Mila into the river of lost souls. Regina and Snow come across a hurt horse and Regina uses her magic to heal it and in doing so she regains control of her magic. Emma, Snow and Regina have their names carved into headstones leaving them trapped in the underworld and unable to perform the heart split to save Hook Hades of course ... Written by ldykailah-186-981870

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.

Gold creates a Storybrooke portal; Zelena and Regina clash; Belle and Rumple are reunited; Snow and David try to send a message from the Underworld to their son, Neal.

Belle turns to Rumplestiltskin with hope of finding a way to protect their child from Hades. However, they disagree over whether to use dark magic, as Belle forbids Rumplestiltskin from using his powers for evil.

In flashbacks, Ruby and Mulan find themselves in Oz, where they meet Dorothy. When the tree of them 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. There, Ruby teams up with Emma, Regina and Snow to continue looking for Dorothy. Meanwhile, Snow and David struggle with not being with their son, Neal, and devise a plan so that one of them can escape the Underworld. Written by Jennifer Percopo

Now that Hades and Zelena are reunited, Hades tells Zelena that he wants a future with her outside of the Underworld. All she needs to do is heal his heart with True Love's Kiss so they can leave the Underworld and trap the heroes there for eternity. When Regina overhears the plan, she 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. Meanwhile, David finally meets James, only to realize that his twin is determined to seek revenge on him for stealing the life he could have had. Written by Jennifer Percopo

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. Meanwhile, Cruella De Vil is determined to keep the heroes trapped in the Underworld. In flashbacks, Emma searches for answers about her family and makes an unexpected friendship.

Emma, David, Regina, Robin and Henry are finally back home in Storybrooke and reunited with Snow, but, unfortunately, they still have to contend with Hades, who continues to deceive Zelena as he lays out his plan to use the all-powerful Olympian Crystal to take over the town. The heroes desperately search for a way to defeat Hades while Hook does the same in the Underworld, looking for those missing storybook pages. Regina and Robin take a more direct approach, which culminates in an epic showdown that will leave our heroes forever changed. Written by Ahmed EL Masry

Regina grieves over Robin Hood's death and Henry sets out to destroy all magic

With the possibility of magic being destroyed and the fate of Storybrooke hanging in the balance, it's a race for Emma and Regina to track down Henry before Gold can find him first. Regina continues to struggle with her frustrations over her former evil-self and, elsewhere, Snow, David, Hook, and Zelena are imprisoned and must contend with two very disturbed individuals that may give Gold a run for his money. Written by Jennifer Percopo