The story starts in Cambridge, at a college where a don is murdered. We, and Inspector Buller, spend a lot of time wondering about how things were achieved, and which of the many clues laid out so invitingly are the details that matter. After the murderer's gloating revelations, Buller goes off to stay with friends in the country, thoroughly depressed about the Cambridge case because he can't see any way to getting an arrest, and he's nervous about the murderer still being at large. Who wouldn't be? This murderer is as animal-like and vicious as any psychopath, and now he has tasted blood. I'm not giving anything away by saying 'he', because there aren't many women in the story, and only one heroine, with whom the Inspector is in love, so she is a natural target for the murderer's dripping hands.