When I see a shipwreck, I like to know what caused the disaster...I learned nothing but the glow that wrapped her face when the soup came. That's the story.
As a rule, said Holmes, the more bizarre a thing is the less mysterious it proves to be. It is your commonplace, featureless crimes which are really puzzling, just as a commonplace face is the most difficult to identify.
When we really sit back with a smile on our face is when we run into a situation we can understand, where the facts are ascertainable and clear, and the course of action obvious.
He is haunted by a demon, a demon against which he feels powerless, because in its first manifestation it has no face, no name, nothing; and the words, the poem he makes, are a kind of exorcism of this demon.