"Operation Mongoose" is a two-part story comprising the twenty-first and twenty-second episodes of the fourth season of the American fantasy drama series Once Upon a Time, both of which aired on May 10, 2015.
In this episode, Isaac becomes a wild card in Gold's scheme to change everyone's destiny as Emma, Regina, Mary Margaret, Hook, and David attempt to stop them.
(Part 2) In our world, 1966, Isaac Heller (the Author) is working at a television shop as a struggling writer trying to sell color tvs, until he gets a letter from Star Publishing saying that he is wanted for hire.
He arrives to find a mostly empty room, with the Apprentice at the desk, who then lays out a selection of different writing materials and demands that Isaac choose one as a test.
Emma, Hook, Henry, Mary Margaret, David, Regina and Robin are in the library of the mansion, searching for a way to stop Gold and Isaac from enacting a new reality with the newly activated ink.
Henry awakens with the key in his hand at the loft, but runs downstairs to find that Hook, David and Mary Margaret have disappeared, along with the rest of the people of Storybrooke.
He then drives himself to a restaurant in search of help, but notices a best-selling book on a shelf: a paperback version of Heroes & Villains by Isaac Heller.
After Henry finds out that a happy ending for a hero in this universe will return things to the reality that he knows, Isaac knocks him out and binds him to a cart, and leaves him to be killed by an ogre.
Using a copy of Isaac's book as a guideline, Henry seeks out Regina, who is living life as a bandit "Snow White" in this reality.
Isaac tells Snow that she can get her happy ending again (which was love with Prince James in this timeline), if she agrees to kill Henry along with Regina.
Ignoring Henry's advice, Regina proceeds to rob the royal carriage, but when she opens the door, she is confronted by Snow.
The two drink to becoming new friends and declare their mutual respect for one another as outlaws in the forest, with Robin offering her leadership of his Merry Men.
As she leaves the bar, she runs into Henry and informs him about the impending nuptials, which he realizes will mark the permanence of the alternate universe when the church bells ring.
Unfortunately, Isaac is there waiting, and tells him that his happy ending will be taken away if a boy named Henry succeeds in his quest to reverse the events of the new book.
Isaac then tells him that he must thwart Henry and Regina's plan to stop Robin and Zelena's wedding in order for him to keep his happy ending.
As the trio escape on the ship, Emma, while getting to know the new Hook, explains that the guard they knocked out was none other than Lily, who has the ability to transform into a dragon.
As everyone awakens from the events back in Storybrooke, Emma runs to Hook and is relieved to find him alive, though she is still unable to admit her love for him.
Meanwhile, as Isaac approaches the town line, he is stopped by Mary Margaret and David, who ask about his motives for messing with stories as the author.
Isaac tells them that a lifetime of bad bosses and others who pushed him around inspired him to hate "heroes" and side with the villains, who he thought never got a break.
The Sorcerer's Apprentice tells Henry more about his new powers as the Author, which do not include the ability to resurrect the dead directly, such as his father Neal, since he died in the real world.
Next season won’t center on our heroes rallying together to defeat some flashy, newly introduced foe based on a classic Disney villain."
)"[6] Amy Ratcliffe of IGN said of the episode, "The Season 4 finale of Once Upon a Time relished in the lighthearted aspects of telling a story set in a fairy tale world while also hitting some emotional notes and developing characters in new ways.
[9] The ending scene with Emma going dark ranked number two in Entertainment Weekly's Season Finale Awards for "Twist You Saw Coming a Mile Away.