“Yes, if you have nothing better to do.” A minute later we were both in a hansom, driving furiously for the Brixton Road.

It was a foggy, cloudy morning, and a dun-coloured veil hung over the housetops, looking like the reflection of the mud-coloured streets beneath. My companion was in the best of spirits, and prattled away about Cremona fiddles, and the difference between a Stradivarius and an Amati. As for myself, I was silent, for the dull weather and the melancholy business upon which we were engaged, depressed my spirits.

“You don’t seem to give much thought to the matter in hand,” I said at last, interrupting Holmes’ musical disquisition.

“No data yet,” he answered. “It is a capital mistake to theorize before you have all the evidence. It biases the judgment.”

“You will have your data soon,” I remarked, pointing with my finger; “this is the Brixton Road, and that is the house, if I am not very much mistaken.”