Well, it depends how and more importantly, why, the transfer is done.
For instance, suppose I want to 'steal' some data like a login from someone. I'd either hack their site and send the request for that site to my site and I'd produce what looks like the real site. It would ask for a logon and p/w info. I'd record it and then send the person off to the real link they wanted. I'd have the data, the person would see another logon request, can't figure out why, but get in on the second attempt.
I don't think that deception was the root cause of what you were asking for myself, just some HTML answer.
However, I assume that you do know who the original author is and where the site is hosted? If you contact the author I guess fixing it would cost you money and that is what you want to avoid? Can you see if you can get the original site's source from him? I'd move it in total and re-do it as I wish.
You can probably save most if not all the source, but I suspect the original author is the owner and might not be too happy with you doing that?