This wasn't good. Sherlock didn't do surprise, Sherlock was the one who did any and all surprising.

"Is there bread in there?" John asked. It was stupid, but between Sherlock's sudden loss of composure and the (somewhat rude) mysterious stranger, it was important that 221B had one stable occupant.

"If you want coffee, I've put on a new pot for--" he stopped short, which was the politest way he could think of saying introduce yourself already.