Sherlock Holmes : Charles Augustus Milverton

Holmes is hired by the débutante Lady Eva Blackwell to retrieve compromising letters from a blackmailer named Milverton who causes Holmes more revulsion than any of the 50-odd murderers in his career. Milverton demands £7,000 (over £800,000 in 2015) for the letters. Holmes offers £2,000 but Milverton insists. Holmes resolves to recover those letters by whatever means necessary.