In "His Last Vow" Mycroft says "here be dragons" in the scene when both Sherlock and Mycroft are smoking. Does that mean he knows about Moriarty? In the popular TV series Sherlock, in season 2 episode 1 "Scandal In Belgravia", when Sherlock is about to be hired by the British Royalty, what does Mycroft mean when he says "I'll be mother" to which Sherlock replies "and there's the whole childhood in a nutshell"?