Just when you thought you were watching Sherlock a wild John Harrison appears. Sherlock, your Khan is showing. <-- exactly what I thought during that scene: the slicked-back hair, the glowering look directed at Mycroft. yep, it's Khan.
Moriarty - did you miss me? I missed the presence of there actually being a bad guy character, though. I do love how in three episodes the whole fandom went from wondering how Sherlock did it to how the heck Moriarty did it.