Okay, this may seem a bit corney, but bear with me: the scientist finds the works of the 'real Frankenstein', who was, in some circles, a known associate of Kemmler. He starts using the book to build a better body, with the idea that he will be using it in the end. However, what he doesn't know, is that the book is actually a powerful magical artifact, which holds the soul of a deceased. After the character's discover this, they will, at first, surmise it is 'Frankenstein', who plans to use the new body to resurrect himself. This might be all the plot you need, but for a nice twist... It's actually one of Kemmler's back-up devices! It would be an older one, from several centuries past, but still nothing to scoff at. This would firmly ground your plot in the 'canon' of Dresdenverse and give your characters an epic scale story to stop the return of one of the most powerful necromancers of all time. For good measure, you could always throw in a mysterious
cowled benefactor with shady motives...
After reading this, please, try not to think of Harry Potter and He Who Must Not Be Named...