After six seasons, the residents of the enchanted forest face their greatest challenge yet as The Evil Queen, Captain Hook and Rumplestiltskin join forces with a grown up Henry Mills and his daughter Lucy on an epic quest to once again bring hope to their world and ours. Along the way, new fairy tale characters and old search for true love, find adventure and once again take sides in the struggle of good against evil, as classic tales are once more twisted and reimagined.

After Regina crushes the heart of her Dark Half, it appears Storybrooke will finally enjoy an era of tranquility. But this reprieve is short-lived when the Evil Queen reemerges and wreaks a level of havoc and terror that makes her previous cruelties pale by comparison. Desperate to right her counterpart's wrongs, Regina fights the ultimate battle against her nemesis, but can one survive if the other is destroyed? Meanwhile, Gold's attempt to win back Belle before their child is born has heartbreaking consequences; Snow and David face a new, even more insidious curse; and just as Emma begins to envision a happy ending with Hook, she discovers she's destined, as the Savior, to die at the hands of a sword-wielding assassin -- unless she can somehow change her fate.

When the Savior becomes the "Dark Swan," the lines between good and evil blur as Emma begins to relish the intoxicating taste of absolute power. Terrified she'll succumb, Emma and Hook visit Camelot to find the one person who may be able to aid them: Merlin. Unfortunately, King Arthur proves treacherous, and when he joins forces with a vengeful Zelena, Emma and Hook's hopes are shattered. Now Emma and her entire Storybrooke family must embark on a chilling descent to the Underworld of Hades, where they'll try to rescue Hook from a fate worse than death... with "help" from Rumplestiltskin. But will any of them survive the journey?