Charles Augustus Milverton

Holmes is hired by the débutante Lady Eva Blackwell to retrieve compromising letters from a blackmailer: Milverton, who causes Holmes more revulsion than any of the 50-odd murderers in his career. Milverton is "the king of blackmailers". He demands £7,000 for the letters, which if given to third parties would cause a scandal that would end Lady Eva's marriage engagement.