The most difficult crime to track is the one which is purposeless.

The sky was of the deepest blue, with a few white, fleecy clouds drifting lazily across it, and the air was filled with the low drone of insects or with a sudden sharper note as bee or bluefly shot past with its quivering, long-drawn hum, like an insect tuning-fork.

I could not rest, Watson, I could not sit quiet in my chair, if I thought that such a man as Professor Moriarty were walking the streets of London unchallenged.

No man burdens his mind with small matters unless he has some very good reason for doing so.

I never can resist a touch of the dramatic.

Dogs don't make mistakes.

It is, of course, a trifle, but there is nothing so important as trifles.