Emma’s (Jennifer Morrison) whole world might come crumbling down in episode 16 of “Once Upon a Time.” The Storybrooke savior has had her ups and downs, but she finally seems to be on the track towards happiness. However, that could all change as Gold (Robert Carlyle) and the Queens of Darkness continue to look for the Author in “Best Laid Plans.”

According to the synopsis for episode 16, Hook (Colin O’Donoghue) will warn Emma that “her fate is at stake.” The pirate discovered the horrifying plan from Ursula (Merrin Dungey) in episode 15. The sea witch explained that in order for the villains to get their happy ending, Emma’s heart had to become filled with darkness … forever. Since Emma is Hook’s “happy ending,” he’ll attempt to do everything in his power to protect her. But will it be enough?

The episode description continues that Regina (Lana Parrilla) will lead the other villains “on a wild goose chase” as they look for the Author. Although they believe that the former evil queen is now on their side, what they don’t know is that August (Eion Bailey) gave her an important piece of information about the mysterious Author – the Sorcerer trapped him behind a door of a piece of paper from the Story Book. As she tries to keep this new clue from the villains, Henry (Jared S. Gilmore) will “make a breakthrough in his search” for the Author.

Unfortunately for Henry and the others, this “breakthrough” might not result in anything. The episode 16 synopsis teases that Mary Margaret (Ginnifer Goodwin) and David (Josh Dallas) will “need a moment to reconsider the best course of action.” If this has anything to do with their secret about Maleficent’s (Kristin Bauer van Straten) child, then Henry might be out of luck completely.

Finally, “Once Upon a Time” fans can look forward to another flashback to the Enchanted Forest. Viewers already know that Snow White and Prince Charming did something unforgiveable to ensure that their child would grow up to be a hero and not a villain. This week, that dark secret will be revealed. Their search for help will lead them to a “kindly old hermit.” It’s there that the pair will be “presented with a choice that could secure their child’s goodness, but at a price that will haunt them for years to come.”

Based on the promo video for “Best Laid Plans,” it looks like Emma might finally find out that her parents aren’t the heroes she thought them to be.

“Once Upon a Time” Season 4, episode 16 will air on ABC on Sunday, March 29 at 8 p.m. EDT. Watch the promo video and sneak peeks below: