"The Final Battle" is a two-part story comprising the twenty-first and twenty-second episodes of the sixth season of the American fantasy drama series Once Upon a Time, both of which aired on May 14, 2017.
In the episode, Henry and Emma work together to defeat the Black Fairy; in the Enchanted Forest, Snow, David, Hook, Regina, Zelena, the Queen, Aladdin, and Jasmine team up to save the worlds from being destroyed.
After running into Archie, he tells Henry that Emma is at the hospital, where she has been committed to a psychiatric ward for the past two years.
Snow, David, Hook and Regina wake up and find themselves back in the Enchanted Forest, specifically at the palace where the events that led to the first curse began.
At the same time in Storybrooke, Fiona brings lunch to Gold and asks that he fixes her watch, as it appears that she is now his primary support in the wake of Belle's "disappearance".
The realms start to crumble under Fiona's curse, forcing all of its survivors to take shelter in the Evil Queen's castle, including Aladdin and Jasmine.
Henry breaks Emma out of the hospital and takes his mother to the rooftop where she was married, in hopes that she will remember her wedding to Hook.
She has glimpses of her memories, but Emma has doubts and tells Henry that she wants to return to Boston, for fear that Fiona will put her back in the psychiatric ward.
Most of the realms depicted in the book begins to be consumed by the curse, which arrives on the outskirts of the Enchanted Forest in the form of a massive storm of dark magic.
When she gets back to her apartment there, she discovers that Henry left her a hand-drawn storybook in order to make her remember their past.
Meanwhile, as the realms are starting to collapse, David and Hook escape the dragon, but while climbing down the beanstalk, they lose their balance and fall.
As the storm closes in, the Queen decides to sacrifice herself and protect the castle, in order to buy enough time for Regina to restore the bean, while everyone else gathers in the courtyard.
She orders Gideon to recover her own wand, which she uses to decipher the mysterious writings that Henry had scribbled, then sends him to kill Emma.
The Enchanted Forest, Neverland, Wonderland, Agrabah, Arendelle, the Land of Oz and all the other realms are restored and their residents embark on their happy beginnings, as does everyone in Storybrooke.
Emma and Hook patrol as the town sheriffs, Henry goes back to school, Regina returns to her role as mayor with the dwarfs giving her the title "queen" without "evil", Zelena spends time with baby Robin, David farms with a growing Neal, Gold and Belle renew their relationship and raise Gideon together, Snow White becomes a teacher again and Robin Hood from the Wish Realm proposes to the Queen in Regina's restored palace.
"The Final Battle" marks the last appearances as regulars of six cast members: Jennifer Morrison, Ginnifer Goodwin, Josh Dallas, Jared S. Gilmore, Emilie de Ravin and Rebecca Mader.
Sean Maguire does not appear in the episode, but is credited, as he lends his voice for a few seconds in a scene with the Evil Queen.
[1] Despite a 25% drop from the fifth season's finale, the episode saw an increase from the previous outing, scoring a 0.9/4 among 18-49s with 2.93 million viewers tuning in.