`` 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 '' '' ? ''