I don't really get the episode The Final Problem in the Sherlock series. But what I find most amazing is that Sherlock who can basically predict the future 2 weeks in advance can't notice that there was no glass between him and Eurus.
Eurus had a mic to mimic the voice inside glass. But what about the violin she was playing? Couldn't Sherlock notice it? And suppose if the violin also had a mic on it like Eurus then when Sherlock played it, why couldn't he figure out that the violin's sound was not right?
I mean I can't just understand that a person so brilliant like Sherlock couldn't figure out that there was no glass behind him and Eurus?