Once Upon a Time’s Evil Queen is one bad, bad witch… She killed her father, squeezed the life out of her lover’s heart and invoked a curse that turned the fairy tale world upside down.

And, you’ll soon get the chance to learn what makes the Evil Queen so vile on ABC’s hit fairy-tale drama.

Lana Parrilla, the 34-year-old Puerto Rican-American actress who plays the Evil Queen, teases the origin of her wickedness springs from one place.

“It’s one particular moment,” Parrilla tells TVGuide.com. “It’s one thing that just explodes and branches off into all these other little things, but its one big f—-up that changes her life.”

“We’ll go back in time in fairy-tale land and see who she was before she became this evil queen,” adds Parrilla. “The big secret will be revealed.”

Before she was sending the Hunstman after Snow White (Ginnifer Goodwin), she was wedded to Snow’s father, King Leopold (Richard Schiff), though their dysfunctional marriage was the catalyst for her hatred of Snow.

“There is an episode coming up where you do see the king and queen together and you can see the hardship between them,” she says. “You learn of how unhealthy and unsupportive that relationship was. How he always favored his daughter more than her.”

Whether she truly loved the king or was just seeking his status is yet to be revealed, but the Evil Queen is apparently capable of love, as we’ll come to learn that she had a previous lover she truly cared for.

“It is someone that you’ve met before,” she reveals. “You see this really soft, vulnerable side to her. Even her voice shifts with a softness to it. She wants to love; it’s just difficult for her. Once she has it, she doesn’t really know how to sustain it or stabilize it.”

Her inability to love was proved when she killed off the only man in Storybrooke who’s ever shown her affection.

“I don’t think she feels good about what she did,” Parrilla says of the Evil Queen’s alter ego Regina killing Graham (Jamie Dornan) in the midseason finale.

“You see a tear coming out of Regina’s eye when she crushes the heart, which, to me, is very telling. You can see that this was not an easy decision for her.”

Once Upon a Time returns Sunday at 8:00 pm ET on ABC.