Once Upon A Time Season 4
Emma and Hook in Once Upon A Time season 4ABC

Once Upon a Time returns with an all new episode tonight, 1 March at 8pm on ABC Network.

Episode 12 is titled, Darkness On The Edge Of Town, where Cruella de Vil, Ursula and Maleficent could wreck havoc in Storybrooke.

Click here to watch the episode via live stream on ABC and click here to watch it online on ABC's office website.

The official synopsis reads as follows:

Gold reunites the queens of darkness. With Gold banished from town, the residents of Storybrooke attempt to resume their normal lives. Hook and Belle search for a way to release the fairies from the Sorcerer's hat, while Emma, Henry and Regina continue to look for clues that could lead them to the Author. But when a terrifying darkness descends on the town, Emma and Regina are forced to confront the true nature of evil. Meanwhile, in New York, Gold and Ursula enlist Cruella De Vil to join their cause

The new teaser, unveiled at the Oscars, has hinted at Emma getting a taste of darkness in the second half of season 4.

While executive producer Edward Kitsis told Variety, "One of the big themes for the second half of the season that we want to deal with is, 'What makes someone a hero and what makes someone a villain?' And what the differences are and what the common ground is."

"Emma has spent a long time in the series being told she's a savior and being told she's a hero, and now she's going to have to face that it's not as black and white as that. I think going into this second half, all of our characters are going to be wrestling with this idea of good and evil, not just in terms of what they're facing as an external threat, but internally and within themselves," Kitsis explained.

He also spoke about Hook and Emma relationship in an interview with Entertainment Weekly.

"What we're trying to do is just show a relationship, a real one, even though it's between Captain Hook and the daughter of Snow White and Prince Charming," he said and added, "What we're going to do is we're going to see them grow and we're going to see them get tested. Like all things, sometimes things get in the way of just purely your relationship; sometimes life gets in the way of it."

Meanwhile, The Queens of Darkness, Maleficent, Ursella and Cruella, are ready to get their wicked revenge and are teaming up to unleash a whole new chapter of hell in Storybrooke.

Watch all the promos here: