Well you don't know why she's here, but she was obviously the victim, being chained up to the wall and all, and considering that her shirt seems to have been removed, the man was probaly planning something nasty.
"Alright, so is there a key or something to the chains he put you up there with?"
The girl just stares at you.
"Hello?"
"Oh, I'm sorry. I thought I was having another hallucination. I would have sworn a raccoon was talking to me."
"Erm. Well. I sort of am, half raccoon, at the moment at least."
"At this point, I don't really care if you can get me down."
You quickly look through the clothes of the former man, and find a set of keys. Using them, you are able to release the girl from her chains.
"Erm, thank you.... I don't, suppose, that you have the gray book he took from me?" The girl ask.
"I do.... Why do you need it?" You ask.
"Well.... Erm... The thing is.... I'm a guy." She responds.
"Wait, what?"
"You see..... Erm... This is going to sound strange, well maybe not considering what I'm talking to.... But, the book is.... Well, it's magic, or it contains magic. They wanted the book. But, I was sort of enjoying it... I had made myself, somewhat muscular, and wanted to keep the book. When I refused to give it to them, they took it anyways, then, turned me into a girl."
"So, you're a guy?"
"Yes, and I need the book to change myself back...."
"I see."
You explain everything you know about the books, including your dreams of Saphira and the spells that are available when combined.
"So, you need the book then? Well.... If you're going to keep it, can you at least change me back into a guy? And possibly give me my muscles back.... I'd really like to knock some heads togethor for what they did to me."
You could probaly change her back to a him, and make her more muscular again, then use her help to find whoever has the Book of Mind. However, it could also make it difficult to sneak in, if there are two people.