Trouble is brewing on “Once Upon a Time.” Last Sunday viewers were reunited with Maleficent (Kristin Bauer van Straten). The dark and powerful witch had died, but Mary Margaret (Ginnifer Goodwin) and David’s (Josh Dallas) blood brought her back to life. Unfortunately for them, she wants vengeance in episode 14.

Mary Margaret and David are used to encountering new and dangerous problems. However, the arrival of Maleficent in Storybrooke is an entirely different situation. Fans discovered in episode 13 that the pair were responsible for Maleficent losing her child in the Enchanted Forest of the past. Now that Maleficent’s returned … she wants to kill their chance at a happy ending. But with Emma (Jennifer Morrison) and baby Neal in their lives now, Mary Margaret and David are willing to do anything to protect their family – even if it means endangering Regina (Lana Parrilla).

According to the synopsis for episode 14, titled “Enter the Dragon,” Regina (Lana Parrilla) will reluctantly agree to help Mary Margaret by going undercover to spy on the Queens of Darkness – Maleficent, Cruella de Vil (Victoria Smurfit) and Ursula (Merrin Dungey). Although she’s desperately trying to put her dark days behind her, Regina will channel her inner evil queen in order to infiltrate the villains. Needless to say, the Queens of Darkness will be suspicious of Regina, and she’ll be forced to “get her hands dirty” in order to fit in.

While Regina gets her evil on, Henry (Jared S. Gilmore) will continue his research on the mysterious Author. He’ll make progress … but will it be too late for Regina by the time they find the Author? A flashback to the Enchanted Forest will give “Once Upon a Time” fans a look at Regina and Maleficent’s relationship prior to Storybrooke.

Elsewhere, Hook (Colin O’Donoghue) will turn to Belle (Emilie de Ravin) to ask for “an unusual favor.” Could it have something to do with his secret connection to Ursula? Or perhaps it relates to Belle’s new relationship with the Knave (Michael Socha)?

“Once Upon a Time” viewers can watch the drama unfold when Season 4, episode 14 airs on ABC on Sunday, March 15, at 8 p.m. EDT. Watch sneak peek videos from “Enter The Dragon” below: