For years, an insidious blackmailer has preyed on the weaknesses of others throughout London. When Holmes hears of the complete misery and suffering this menacing mystery man is creating, he goes on a campaign to thwart his evil scheming. Even Dr. Watson is astonished by the strangeness of Holmes' crusade to expose "the worst man in London" in "The Master Blackmailer", a case that also finds Holmes falling in love.