The title logo is attached to a flying dirigible.
At Granny's, Regina is in mourning during a wake for Robin. Snow and David are ready to console Regina and even Zelena is ready to reach out each other in the wake of her loss to Hades. Violet also pays respects to Robin as she tells Henry she was worried about him while he was in the Underworld. At the Clock tower Gold is looking for a way to find another way to wake up Belle, and begins to look at the Olympian Crystal, which he'll use to tether all the magic from Storybrooke. Gold holds the crystal and it glows. Back at the Diner, Emma wants to talk to Regina but suddenly they hear a noise, and witnesses a series of light power outside from the olympic crystal. All of a sudden Hook shows up as Emma tells Regina about his return. Realizing that Gold is behind it, everyone traces the disturbance to the tower where they find Belle, but Emma tells Regina to let her and the others handle this one, leading to the two bickering until Henry stops them, but after Regina disappears, Emma tells Henry to leave as well, only to meet up with Violet at the Pawn Shop. Henry is upset over how magic has destroyed his family and sees it as bad, so he comes up with a solution by creating a plan called “Operation Mixtape.” Utilizing his role as the Author, Henry uses the quill to writes himself as the possessor of the crystal, and suddenly, it appears in his hand. He sends both mothers a text, detailing his plans.
When Gold tells the others that Henry has taken the crystal, he tells them that Henry could destroy all magic and with it, Storybrooke. Emma notes she placed a GPS app on Henry’s phone to find him, but Henry had the phone left behind on the bus on purpose. At the same time, Zelena uses The Sorcerer's wand and creates a portal door to get Merida and the other visitors out of Storybrooke just in case magic does get destroyed. Unfortunately, the portal becomes too strong that it dragged Zelena, Snow, David, and Hook into it because of the magic tied to the crystal closed it when the portal door vanished in thin air.
Regina and Emma are looking for Henry and Violet in Boston, but they weren't on the bus, as Henry left it on board because he knew Emma placed the GPS tracker app on it. After she shows the lady the picture of Henry on her flipphone, Regina grabs Henry's phone in the trash on fire, and Emma makes it go away. They also discover that magic can work outside of Storybrooke, as Henry has taken the crystal and the magic. Regina then uses a needle on Emma's bloody finger on the map where to find Henry and Violet, leading them to New York City.
In The Unknown Universe
Zelena, Snow, David, and Hook soon find themselves in a realm of a new world, but Zelena has no way to return as her wand broke upon arrival. The foursome come across a frightened gardener who warns them they shouldn't be there, only to have another man appear and using magic to knock the unwanted visitors out. Hours later they wake up in a cage of enchanted bars and is greeted by the warden, who believes that the Dark One must have sent them; they are enemies. The gardener visits the foursome, who agrees to help them if they take him to Storybrooke. After Zelena gives the gardener her broken wand to repair it, their attacker, Poole, finds the gardener and takes Zelena's wand, then pours a blue potion down his throat and suddenly turns into the warden himself. It turns out that gardener is actually Dr. Jekyll and the warden is Mr. Hyde, who suddenly created a portal, where it arrives to Storybrooke and throw a wrench into Gold's plans to free Belle from Pandora’s Box by pulling it through the portal. Hyde plans to blackmails Gold to cooperate with him if he ever wants to see Belle again.
In New York City
In New York City, it's discovered that Henry and Violet have arrived there, as Emma’s blood traced them to Henry but it also leads Gold to his whereabouts. At Neal's apartment, Henry admits that his father was trying to destroy magic before he died, so they make plans to find his journal. Moments later, Regina and Emma shows up to the place, and Regina suddenly encounters an old letter from Robin addressed to her, reminding her that she will always be the brave heroine with whom he fell in love. Regina admits that she will never be at peace with herself as she wondered should she become the Evil Queen again because she feels cursed and will never find redemption, realizing that the more good that she does, the more people she loses. And before Emma can convince her, darkness has started to consume Regina again, unaware that Gold was listening to Emma and Regina's conversation.
At the library, Henry and Violet look for more answers and Henry finds multiple Once Upon a Time storybooks containing different stories. Violet then sees a duplicate of the Holy Grail, which was said to hold all magic. Henry breaks the glass, steals the item and stashes it in his bag. Gold then catches up with them, puts them both to sleep and leaves with the crystal. Emma and Regina later find Henry and Violet, but Henry leaves out the part about finding the Holy Grail, realizing that their magic is ineffective again, due to Gold's actions. Regina uses a needle on Henry's finger to find out whether Gold is still in New York. Henry's bloody finger on the map but the magic isn't working, because Gold is at the Hotel.
- Ginnifer Goodwin as Mary Margaret Blanchard
- Jennifer Morrison as Emma Swan
- Lana Parrilla as Regina Mills
- Josh Dallas as David Nolan
- Emilie de Ravin as Belle French (absent)
- Colin O'Donoghue as Hook
- Jared S. Gilmore as Henry Mills
- Rebecca Mader as Zelena
- Sean Maguire as Robin Hood (voice)
- Robert Carlyle as Mr. Gold
- Lee Arenberg as Leroy/Grumpy
- Beverley Elliott as Granny
- Amy Manson as Merida
- David-Paul Grove as Doc
- Gabe Khouth as Sneezy
- Faustino Di Bauda as Sleepy
- Michael Coleman as Happy
- Mig Macario as Bashful
- Raphael Alejandro as Roland
- Michael P. Northey as Friar Tuck
- Jason Burkart as Little John
- Olivia Steele Falconer as Violet
- Hank Harris as the Groundsman
- Arnold Pinnock as the Orderly
- Sam Witwer as the Warden
- Candus Churchill as Librarian
- Chris Olson as Toll Operator