The Adventure of Charles Augustus Milverton Sherlock Holmes

"I'll tell you, Watson. He is the king of all the blackmailers. Heaven help the man, and still more the woman, whose secret and reputation come into the power of Milverton! With a smiling face and a heart of marble, he will squeeze and squeeze until he has drained them dry. The fellow is a genius in his way, and would have made his mark in some more savoury trade. His method is as follows: He allows it to be known that he is prepared to pay very high sums for letters which compromise people of wealth and position. He receives these wares not only from treacherous valets or maids, but frequently from genteel ruffians, who have gained the confidence and affection of trusting women. He deals with no niggard hand. I happen to know that he paid seven hundred pounds to a footman for a note two lines in length, and that the ruin of a noble family was the result. Everything which is in the market goes to Milverton, and there are hundreds in this great city who turn white at his name.