Based on the story of the faithful servant boy as retold in the folk song "Love Can Enter an Iron Door", which is very worth a listen.
And oh look, I wrote a love story.

Many thanks to pocochina and rirenec for the encouragement.

Love was weakness, Cora knew. She had manipulated everything to turn her daughter into a queen. That had been her plan, since the time long ago when she'd arranged her own wedding as a miller's daughter to a prince. She'd made it happen, for herself and for her daughter. And now Regina, the poor sweet girl, had fallen in love. With, no less, a stable boy.

Cora knew what love was. She remembered it, vaguely, remembered giving herself to a dark magician on a stone floor surrounded by gold thread that had been spun from straw. She remembered liking how it felt. It was so long ago, back when her heart was still in her body. Really, she could barely remember it. What Cora wanted for her daughter was the same kind of marriage she had chosen for herself: separate bedrooms, separate lives, and a great deal of political advantage. So when the girl, Snow White, told her that Regina still wanted to marry Daniel there was only one thing to be done. She put Regina in a dungeon. "You'll stay here until you come to your senses," she said. "It's for your own good." She thought about simply removing Regina's heart, it would make things easier, help her make the correct choice between love and power. But the memory of when she'd done that to herself wasn't pleasant. The dungeon, she thought, might be kinder. Cora remembered what imprisonment had done for her, how it had strengthened her resolve, her determination to achieve power and revenge. For her daughter it might do the same.

"I found a way to get you out," Daniel whispered to Regina between the bars while she pressed her lips against his hand. There was a part of her that had hoped he escaped, she'd begged him to flee when she heard her mother was coming, but she couldn't suppress the joy she felt at seeing him again. "Look, I have the key," he said, showing it to her.

Regina couldn't imagine how he'd gotten it, what he had to do, who he had to bribe. It didn't matter, though. "My mother will know I'm gone. She'll find me, instantly."

"Not if I take your place," Daniel said. He picked up a small bottle and swirled the liquid inside it. "You won't believe what I had to promise to get this. Or to whom. But never mind." He took one long drink from it, and in a flash he was transformed into a double of Regina herself, dressed in the same blue gown. "You need to drink too," he said.

Regina took the bottle, held it for a moment, then drained it. A swirl of smoke covered her, then she looked down to see a man's body - Daniel's - dressed in stable-boy's clothes.

"My horse is outside," Daniel said. "Take it and go." He opened the iron door of her prison and pressed a kiss on her forehead, long and slow and sweet.

"I can't leave you," Regina said. "What will happen to you?"

"I'll pretend I'm you. I'll tell your mother whatever she wants to hear, I'll tell her I'll marry whomever she likes, and then when I can I'll get away and find you. Please, my love," Daniel said in her voice. "There's no other way. You have to go know, before we're seen. I'll meet you at the port city. Promise you'll do what I say."

"I promise," Regina said. He was her happiness, he was the choice she had made. She would flee, and wait for him, and they would be together.

"I'll send word soon," he said. "I promise." She kissed him one last time, quickly, and ran off into the night.

For the next two days Cora let her daughter sit in prison. The guards fed her thin gruel and gave her occasional slaps and insults as per Cora's instructions. On the third day she went down in the morning with homemade bread, loudly upbraided the guards for their mistreatment, and asked Regina if she was finally willing to see sense and marry the king.

"I'll marry whoever you ask," Regina said.

It was clear immediately that something was off, and Cora damned herself for a fool for leaving the girl alone. Her daughter didn't speak like this, not in such a cowardly and servile way. Cora raised her hand in a quick gesture and channeled her annoyance with her daughter into a dispel magic curse. The magic was stronger than she had expected, and for a moment she thought her quick spell wouldn't be enough, but then Regina shimmered and smoke rose around her and Daniel was standing before her in the dungeon.

There was magic, Cora knew, in love. This boy had tricked her, and she had been fool enough to let him "Where is my daughter?" Cora shouted. This was the ruination of everything, the destruction of all her plans. She should have killed Daniel when she first discovered him.

"Gone," Daniel said. "Far away. You can't reach her. She's free from you now. I've freed her."

"I'll find her," Cora said, "and you're going to help me." With a flick of one finger she lifted him up into the air, then sent blows to each side of his head.

Daniel endured the strikes like they were nothing to him. "Do what you like to me," he said. "You don't have Regina, that's all that matters."

It took Cora aback, reminded her that there was a time when she would have understood this, when privations endured for love would have felt entirely reasonable. She wanted to torture Daniel until he was dead but something inside her was keeping her from doing it. Perhaps even the memory of love was still making her weak. "Do you love her so much?" she asked.

"So much," Daniel said, dangling in air, his face red from the blows she gave him. He looked her right in the eyes, completely unafraid. "This is how much I love."

Cora recognized the intensity of love in Daniel's eyes. She had seen something like it in the eyes of her dark magician so many years ago, and even without her heart she couldn't bear to look at it. "Flog him," she said to her guards. "See if you can get some information about my daughter." She withdrew her magic and let Daniel fall in a heap on the floor.

Alone in her room Cora tried all her finding spells to locate her daughter. She could tell Regina was still in the kingdom, she found hints of her in various directions, but some strong magic was blocking Cora's ability to find her, let alone bring her back. There was something making her weak, Cora could tell. Perhaps it was the memories. She called guards to her room and ordered them to send out riders to seek out Regina in the directions Cora had found. The ability to give orders was also a kind of power. She would win this, Cora knew. She would have her daughter back, and her daughter would become Queen.

There was something freeing, Regina found, about having the appearance of a stable boy. No one stopped her as she rode for the port city, and it was easy to pick up odd jobs and find places to stay. She could be happy like this, as long as Daniel was with her.

When days passed and Daniel did not come Regina began to worry. She had never studied the magic her mother had wanted to teach her, had found it disgusting, but she started to wish she had, since it would have given her a way to go up against her mother and find Daniel. There might still be time to learn. She had almost resolved to find a teacher when Daniel appeared, riding furiously, and threw himself off the horse into her arms. One kiss dissolved the enchantment, giving Regina back her own form, but she barely noticed in the overwhelming joy at Daniel's escape.

"How did you do it?" Regina asked, after a long time, when she could tear her mouth from his and her attention from her bliss at their reunion. "How did you escape the dungeon? And how did you take back your own form?"

"Dungeon?" Daniel asked, bewildered. "And I've always had this form. What…"

"Tell me what happened to you," Regina said, clinging to Daniel urgently. This man in her arms was most certainly Daniel, their True Love's Kiss had proven it. What, then, had happened in the dungeon? "Tell me how you got here," she said.

"Someone came to me in the stables and told me you'd been imprisoned but that he disguised you as me to get you out. He told me to hide for three days and then come here. That's all that happened. Oh, and he told me to give you this." Daniel held out a small piece of paper, which Regina unfolded with trembling hands. On it were written two lines:

Now you owe me.
And I intend to collect.

The first thing Cora felt when she awoke was the ache of her daughter being gone. It hurt like a deep, piercing pain, like a hollow emptiness in her…in her heart. It was in her chest. It shouldn't be, but it was. It was clearly the doing of the man standing near her bed, by her open window, who despite his deceptive appearance was most absolutely, definitely, not Daniel.

"You'll see your daughter again," he said, with a little laugh. "Don't worry. Perhaps she and Daniel will even invite you to their wedding." Then he shifted to his natural shape and he was as beautiful in starlight as the night years ago that Cora had sent him away, the light on his silvery skin making him shine like the magical creature he was. It was all Cora could do to keep from reaching for him, so she reached inside, grabbing at her heart, to find it blocked with magic. She could break it but she needed time, and needed not to feel like her skin was translucent and her body on fire, like everything about her was vulnerable to Rumplestiltskin's eyes and yearning for his touch.

"Why did you do it?" Cora asked, keeping the tremor from her voice. "Why did you take my daughter?"

Rumplestiltskin shrugged. "I simply took what was mine. We made a bargain you know, dearie."

"A bargain we changed," Cora said.

"Under false pretenses, with you acting deceptively. I don't believe that counts."

"So," Cora said. "Ownership and revenge." The ache in her heart kept growing, and Cora wondered if it was possible to die from this kind of pain. The longing for revenge was a powerful emotion, and perhaps after all that had passed between them it was the only one he had left for her. And yet…ithis is how much I love/i, he had said to her in the dungeon. "Is that all?" she said, and this time she didn't try to keep anything out of her voice, not any of the longing, or the desire, not everything that had been in her heart for all those years it sat in a box without lips to speak what it felt. The last time she had stood before him with her heart still in her body she had been certain that running away with him would make her happier than ever becoming queen, and she couldn't help but still feel it now, and she let him see everything she felt.

He responded instantly, his eyes softening, smirk of victory transforming into a gentle smile, with a longing in his face reflecting hers, and in that moment she knew she had him. Love was such foolishness, such hope. "No," he said. "That is not the only reason." Love had weakened her, but it had weakened him as well. She could use it against him, could manipulate him to get her daughter back. And no, that was not the only reason that she stood and took one step towards him, and then another, watching the hesitancy of his indrawn breath. Something had broken through all the doors and dungeons that she had built around herself and now that it was here she wasn't going to let it go. She stretched out her arms and stepped into the sweet, terrifying embrace of the only man she has ever truly loved.