Arthur Conan Doyle, via Holmes, clearly has his own notions about grotesqueness, as this excerpt from The Adventure of Wisteria Lodge reveals:
I find it recorded in my notebook that it was a bleak and windy day towards the end of March in the year 1892. Holmes had received a telegram while we sat at our lunch, and he had scribbled a reply. He made no remark, but the matter remained in his thoughts, for he stood in front of the fire afterwards with a thoughtful face, smoking his pipe, and casting an occasional glance at the message. Suddenly he turned upon me with a mischievous twinkle in his eyes.
"I suppose, Watson, we must look upon you as a man of letters," said he. "How do you define the word 'grotesque'?"
"Strange--remarkable," I suggested.
He shook his head at my definition.
"There is surely something more than that," said he; "some underlying suggestion of the tragic and the terrible. If you cast your mind back to some of those narratives with which you have afflicted a long-suffering public, you will recognize how often the grotesque has deepened into the criminal. Think of that little affair of the red-headed men. That was grotesque enough in the outset, and yet it ended in a desperate attempt at robbery. Or, again, there was that most grotesque affair of the five orange pips, which let straight to a murderous conspiracy. The word puts me on the alert."
"Have you it there?" I asked.
He read the telegram aloud.
"Have just had most incredible and grotesque experience. May I consult you?
"Scott Eccles," "Post Office, Charing Cross."
"Man or woman?" I asked.
"Oh, man, of course. No woman would ever send a reply-paid telegram. She would have come."
Mr Eccles arrives, most disturbed, in a state of dishevelment.
"I have had a most singular and unpleasant experience, Mr. Holmes," said he. "Never in my life have I been placed in such a situation. It is most improper--most outrageous. I must insist upon some explanation." He swelled and puffed in his anger.
Before he has a chance to explain, the police arrive. They suspect him of murder.
You will have to read the rest of the story here to find out what happens. It is quite spooky.
This example has been cited quite a few times, usually in the introductions to books on the grotesque, and particularly in those sections dedicated to exploring the myriad ways of defining grotesqueness. Holmes' definition fits with more sinister ideas about the grotesque, those involving "the tragic and the terrible." It is "something more" than strange.
I must confess that Hercule Poirot is by far my favourite detective, but Holmes earns my love for his comment that "the word [grotesque] puts me on the alert." We have that in common.
Criminal and academic investigations are not entirely different...
One must be wary of getting too carried away with incidental details. Although, these are sometimes crucial.
You should try not to over-complicate matters and confuse yourself. These things can spiral, you know.
And avoid assumptions. Their success depends upon everything going your way, which will rarely (never) happen.
I'm doing the evil voice right now.