Once upon a time there was a girl. Her mother died shortly after she was born and not long after that her dad remarried. He remarried a beautiful and kind woman who served as the girl's stepmother. The stepmother was not remotely evil, indeed she loved the girl like the daughter she knew she could not have.
Time passed, and the girl grew up. She found that she could no longer remember her mother at all. This made her very sad.
But when she asked her stepmother about her mother, the stepmother just sighed and gave her one of those disappointed looks. So the girl asked her father.
Her father looked even sadder than the girl's stepmother had. "Once upon a time there was a boy," he said. "And this boy believed in love at first sight. But his parents believed in marriage for duty. It was very sad indeed."
"What happened?" the girl asked.
"The boy married who his parents told him to," her father said. "But it didn't turn out very well."
"Why not?" the girl asked.
"Well, first he had a beautiful daughter. Then it turned out that his wife had made a bargain with fairies to give that daughter away."
The girl's eyes grew very large, but she didn't say anything. "Was the wife's life in danger?" she asked.
The father sighed. "Probably," he said.
"Oh," said the girl. "Does that mean that I'm a Changeling?"
The father frowned, because he wouldn't have started this story if he thought his daughter was old enough to know from the beginning what he was saying. "Do you feel like a Changeling?" he asked.
She frowned at him. "I wouldn't know," she said.
Then the stepmother entered the room. "You're not a Changeling, dear," she said, with a sharp look at her husband.
"Right," he said. "Absolutely not. But you might have been. But I, er, the man in the story, thought he could find a way to save his daughter."
"Is that why she died?" the girl asked.
The stepmother patted the girl's hair. "She didn't die, sweetie," she said.
Now it was the father's turn to glance at the stepmother.
"The initial bargain was a fairy child for a human child," the stepmother explained. "But your mother was always over-enamored with fairy lore, hence why she considered offering her first-born in the first place."
"So the fairies offered a change to their first bargain," the father explained. "Instead of fairy child for human child, it was fairy woman for human woman."
The girl glanced at her stepmother. "So she went to fairy land so you could come here?" she asked.
The stepmother nodded, and her husband reached out his hand to offer her reassurance, though he didn't have to. The girl threw her hands around her stepmother, to hug her. "I'm glad you did."
The father waited until his daughter had left the room to frolic in the field or do whatever it was girls did before he turned to his wife. "Are you sure she's not fairy?" he asked. "She picked up on that awfully fast."
"I'm sure," the stepmother said, as in the background there was the loud noise of something breaking, though the father had no idea what there could be outside that would break. "She's definitely all yours."