Take the book you found at Sven's farm and show it to townsfolk in Darkshire.
I must know who was that skulker in the shadows I saw the night my family was killed!
Please, [player], you have shown your resourcefulness. Please find that shadowy figure. I must learn what secrets he holds!
I do not have clues that you do not already know, but here - take the book you found at my farm. Perhaps some of the townsfolk can link this book with its owner.