"I'm asking you to conseedar" (his accent became more Aberdonian as he lost himself in his argument) "I'm asking you to conseedar what it involves if you suppose that this gun was ever brought into the house, and that all these strange things were done by a person from outside.

Oh, man, it's just inconceivable! It's clean against common sense! I put it to you, Mr.
Holmes, judging it by what we have heard." "Well, state your case, Mr.Mac," said Holmes in his most judicial style.
"The man is not a burglar, supposing that he ever existed.

The ring business and the card point to premeditated murder for some private reason.

Very good.

Here is a man who slips into a house with the deliberate intention of committing murder.