There’s the scarlet thread of murder running through the colorless skein of life, and our duty is to unravel it, and isolate it, and expose every inch of it.

“Wonderful!” I ejaculated.

Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.

You say that we go round the sun. If we went round the moon it would not make a pennyworth of difference to me or to my work.

[ The first encounter between Sherlock Holmes and Dr. Watson :] “You have been in Afghanistan, I perceive.”

“How on earth did you know that?”

It is a capital mistake to theorise before one has data.

Of all the ruins that of a noble mind is the most deplorable.

It’s every man’s business to see justice done.