He knows, if he knows anything, that he will have a deeficulty in making his escape, as the house is surrounded with water.

What weapon would he choose?
You would say the most silent in the world.

Then he could hope when the deed was done to slip quickly from the window, to wade the moat, and to get away at his leisure.

That's understandable.

But is it understandable that he should go out of his way to bring with him the most noisy weapon he could select, knowing well that it will fetch every human being in the house to the spot as quick as they can run, and that it is all odds that he will be seen before he can get across the moat?
Is that credible, Mr.
Holmes ?" "Well, you put the case strongly," my friend replied thoughtfully.
"It certainly needs a good deal of justification.