Melody could remember the first time she was told she was to marry the Duke. She was happy. After all, he seemed to be a good man, who cared about the people. There were worse matches. Unfortunately though, that was just a show he put on. It wasn't until they were married and he had her in his grasp that she saw his true colors. He was a horrible man and worse husband. The servants were terrified of him, but not nearly as much as she was after a few months of her living there. In the beginning, she made the mistake of thinking that she had the run of the place so she explored her new home.
When he found her, he beat it into her that she was only allowed where he wanted her. That turned out to be the room he had given her. It was a small room on the top floor with just a bed, a chair, and a bookshelf. Mistake number two, was when she tried to request more comfortable furniture. She was "told" to be more grateful for whatever it was he gave her.
So, that's where she lived her life, locked away in her sad little room with only the books on the bookshelf to keep her company. They were dreadfully boring as well. The servants came in to take care of her business, but none spoke to her. Only her husband on his visits to her and those visits she dreaded. She gathered the courage one day, when she knew he was going to be gone for a few days, to take this chance to escape.
This is where the story would start. I'm thinking that she escapes and when he finds out, he hires your character to go find her. Her husband pretends to worry about her, offers a lot of money for her safe return. So, when your character does find mine and goes to haul her back, she has to somehow convince him to not take her back.
I'm thinking of a romance budding between her and your character.