Sherlock's on the case as his world begins to crossover with the Moriarity Brothers and their underworld machinizations. Both groups find themselves entangled with Irene Adler, a courtesan with high-ranking clientele. Her latest actions threaten the British Crown as we see Sherlock's brother Mycroft hiring Albert Moriarity with retrieving classified information and silencing Adler permanently. Meanwhile, Irene hatches a plan to endear herself to Sherlock in the hopes of preventing her assassination. Sherlock's on the case as his world begins to crossover with the Moriarity Brothers and their underworld machinizations. Both groups find themselves entangled with Irene Adler, a courtesan with high-ranking clientele. Her latest actions threaten the British Crown as we see Sherlock's brother Mycroft hiring Albert Moriarity with retrieving classified information and silencing Adler permanently. Meanwhile, Irene hatches a plan to endear herself to Sherlock in the hopes of preventing her assassination.