I was going to finish the parasite quest to save the rat scientist from the pit. I made a new game save today and can load it and play it normally. I just can't play the old save files. Id rather not have to play through all of that again if I can avoid it.
Your save files are from too many versions back and isn't compatible anymore. If you're on desktop though, you can navigate to the folder with the missing file, and put a dummy file in there to trick the game into thinking everything's fine. Then just save your game and it should work.
