Once Upon A Time Season 4 episode13
Snow White and Charming have been hiding a secret from Emma in Once Upon A Time OnceUponATime/Facebook

Once Upon a Time season 4 returns with an all new episode tonight 8 March at 8pm on the ABC Network.

Episode 13 is titled Unforgiven, where Snow White and Charming are in a dilemma whether they should reveal a secret to Emma.

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 of Unforgiven reads as follows:

Meanwhile, Kristin Bauer van Straten, who plays Maleficent has teased a connection with the Charming family.

"There is a very surprising history," Bauer van Straten told ET Online when asked about Maleficent's ties to Snow White [Ginnifer Goodwin].

"The theme of this season is that many of the characters are playing with that slippery slope between good and evil," Straten added.

While Snow White and Charming struggle on deciding whether to tell their daughter the truth in the upcoming episode, executive producer Edward Kitsis told Entertainment Weekly ."[Emma's] done a lot of growing over the three and a half seasons, so what happens when you find out that the person that was helping you grow might actually be as bad as the people you were trying to get away from?"

The secret may actually push Emma closer to Regina. And executive producer Adam Horowitz teased, "Given what Emma is starting to go through and what Regina has gone through, there's a new common ground between the two characters that will help build on that friendship."

"In addition to Henry, they now have something else they can share and deal with," he added.

Check out the promos below to know more about what could happen in Once Upon A Time season 4, episode 13.