The theories which I have expressed there, and which appear to you to be so chimerical are really extremely practical--so practical that I depend upon them for my bread and cheese." "And how ?" I asked involuntarily.
"Well, I have a trade of my own.

I suppose I am the only one in the world.

I'm a consulting detective, if you can understand what that is.
Here in London we have lots of Government detectives and lots of private ones.

When these fellows are at fault they come to me, and I manage to put them on the right scent.

They lay all the evidence before me, and I am generally able, by the help of my knowledge of the history of crime, to set them straight.