Before the Curse
Snow White's mother Eva falls ill with a mysterious illness. Desperate to help her mother, she turns to magic. Johanna, a royal servant, tells Snow White of a secret of her mother's, the Blue Fairy. When Snow White goes into the woods, she has trouble finding her; suddenly she turns around to find this fairy behind her. The fairy tells her that although it is against the rules, she will give her a way to save her mother. She summons a candle and advises Snow to use it. There is a catch though: she tells her that to save a life, she must take one. Snow must whisper the name of the victim while placing the candle over them. The Blue Fairy also tells Snow White never to speak of it again. Although it could have been used, Snow White cannot bring herself to kill. She tells her mother about it, and Eva tells her daughter that she is proud of her for not taking a dark path. After speaking with her daughter, Eva dies. After all mourners of Eva's funeral leave the hall, Cora appears before the bier. She speaks to Eva, saying poison suits her, revealing she poisoned Eva to death. In actuality, the Blue Fairy who gave Snow White the choice to save her mother with the enchanted candle was Cora in disguise trying to lure Snow White into doing something impure.
After the Curse
Mary Margaret and David help shelter a wounded and dying Mr. Gold after he gets back to Storybrooke with the use of Hook's ship. When Mary Margaret opens the cabinet to grab a blanket for him, she sees the same candle she was given in the Enchanted Forest as Snow White. He tells her he is saving it for a rainy day. Because he is so severely injured, and Cora has his dagger, he asks Mary Margaret to use it to kill Cora and save him. She asks him why she would use it for him when she did not use it on her own mother. Mr. Gold brings up his newly discovered connection to Henry, as his grandfather. It seems like an impossible task for Mary Margaret, but Mr. Gold tells her that she can use the candle over Cora's heart, because it is no longer in her chest, then place it back in her body. During a battle with Cora and Regina pinned against David, Emma, Neal, and Mr. Gold, Mary Margaret runs out of Mr. Gold's shop and into Regina's Vault to find Cora's heart. She lifts the heart out of its box, and as she holds the candle over it, whispers Cora's name thrice. Back in the shop, Cora can sense someone has gotten to her heart. She requests that Regina go check. When Regina gets to the vault, she demands the heart back from Mary Margaret. But, Mary Margaret deceives Regina by playing the part of wanting to bring Regina closer to her mother. She is aware Regina has never truly felt her mother loves her, and that is because she does not have her heart. Mary Margaret suggests if Regina puts the heart back, Cora can love her truly. Regina accepts and rushes back to insert her mother's heart just before Cora can kill Mr. Gold. Cora smiles and hugs her daughter, but collapses soon after. Mr. Gold is healed of his wound and regains his full powers as the Dark One. Regina is horrified and accuses Mr. Gold of having done some trick to steal her mother's life. Mr. Gold brushes off her accusation just as Mary Margaret runs in telling Regina not to put the heart back, but it's too late. Infuriated, Regina looks up in rage at the culprit of her mother's death--Mary Margaret.