The Madness of Miss Grey by Julia Bennet

Everyone thinks Helen Grey is mad but, despite ten years imprisoned in a crumbling Yorkshire asylum, she’s managed to cling to sanity. When a new doctor arrives, she sees an opportunity. William Carter may seem like an honorable man but she’s sure he’ll prove easy to seduce…and trick into helping her escape.
Will would never bed a patient, no matter how tempting she might be. But once he realises Helen’s been imprisoned for no good reason, he’s determined to save her. They need to work together but freeing her won’t be easy, not when her mysterious benefactor is determined to keep her locked up and hidden from society forever.

When Helen is entangled in her own trap and begins to fall for Will too, she must fight not only for her liberty but for her right to love.