For years, a blackmailer has been preying on the weaknesses of others throughout London. When Holmes hears of the utter misery this mystery man is creating, he adopts a campaign to thwart his evil scheming. The campaign astonishes Dr. Watson by its strangeness and finds Holmes falling in love.
Holmes and Watson attempt to thwart the schemes of the infamous blackmailer Charles Augustus Milverton from blackmailing Lady Eva Blackwell. But things do not seem as easy as they do and Holmes must sacrifice his morality and his honourable career to stop Milverton from wrecking her marriage. Holmes and Watson are called in to deal with a blackmailer. A dazzling young lady is about to be married, and Charles Augustus Milverton, the slithery king of all blackmailers, has letters she wrote to another man. Watson is astonished when Milverton calls at Baker Street at the invitation of Holmes, who has a plan to thwart him. As ever, things are not quite as they appear to be.