A flashback shows younger Emma getting ready to record a song. A fellow orphan tells her that no one will ever want to hear her sing. She'll always be alone. Emma crumbles the song.
In present day Storybrooke, Emma's trying to decide between two wedding dresses. Snow offers to let her wear hers.
Another flashback, this one to the Enchanted Forest, finds Snow White wishing on a shooting star to be able to help Emma find her happy ending. The next morning, Snow and Charming wake up, and find themselves singing rather than talking. They sing a song about love being the most powerful magic.
Snow gives Emma her wedding dress, but when she unwraps it, it turns black. The Black Fairy arrives. She sends them to the clock tower to see what she's planning. Snow, Emma, Regina, and Zelena discover enough black fairy dust for a curse. It's going to trigger when Emma and Hook are married. Regina and Zelena team to find a way to stop it.
In the Enchanted Forest, the Evil Queen is furious as she watches everyone singing about love. She sings a song about love not standing a chance against her magic.
Killian and Charming are prepping for the wedding when Emma arrives. She tells Killian the Black Fairy wants her heart. He's ready to help. She insists she needs to face the fairy alone. Killian realizes she came to say goodbye to him.
Back in the Enchanted Forest, Snow and Charming seek out Captain Hook. They want passage on his ship to go after the Evil Queen. He sings a song of revenge. They offer to trade the Dark One in exchange for his help.
Killian goes to Gold's shop. attacks Rumple with Dream Shade. Not to kill him, but to make sure he can't help his mother. The Black Fairy arrives to save her son.
Henry tells Emma she's doing the right thing. She's reminding herself what she needs to fight for by looking through old memories.
Regina and Zelena decide the answer to stopping the curse is to take the time element out of it. In another flashback, Zelena watches Rumple questioning whether he chose the right witch. She sings about wicked always winning while she creates a spell to help Regina. Rumple arrives in present day and stops Regina's plan to end the curse.
The Black Fairy has frozen Emma's family, leaving her alone. Emma tells Henry that she's going to give her what she wants, her heart, so that at least Henry will have everyone else. Henry finds another page in the book. In the final flashback, the Blue Fairy arrives after Regina stopped the singing. She tells Snow and Charming the songs were never for them. They won't remember it happened. But the magic is for Emma and a battle she will face.
Henry helps Emma realize the magic's been inside of her all along. She sings about love and having it with her all along. It frees her family. Emma and Killian exchange their wedding vows in front of their friends and family. Emma calls it a happy beginning rather than a happy ending. Everyone celebrates until the clock strikes six, and the Black Fairy's curse begins to spread. Emma's confident they will win no matter what.