At the beginning of episode 5, right after you've completed Flashback 5, Kate let's you out of the cell. Once she does, walk out of the door and immediately on your left there is a book case. A Turn of the Screw is the name of the book that you need to photograph; and it will be glowing. Simply snap a picture of it.
The attached video shows how to do it and the Radzinsky achievement (I did not make nor do I take credit for this video. Video was made by YouTube user SaggDog7):