The story begins with a late-night discussion between the narrator, Mr. Otway, and his friend Philip Bennion, over [Thomas De Quincey’s essay] “Murder Considered as One of the Fine Arts.” […] Otway finds himself in a position to examine this theory when, the next morning, Bennion is found dead on the floor of his apartment, seemingly of natural causes. In light of the previous night’s odd discussion, Otway is not so sure, and begins to investigate.

… there is a large list of suspects: Raymond Clinton, the no-good nephew of Bennion; Nina Macrae, Bennion’s ward; and her fiancé Ralph Hardwicke. Most surprising of all is that Otway cannot rule himself off the list of suspects: he is a somnabulist, and recalls a singular dream in which he watches Bennion die!