User blog comment:Barry19/Missy theories!/@comment-24825392-20150226174415/@comment-24825392-20150226174959

I think Missy being the killer would be a massive plot twist and would add even more hatred to her character. I also think it would be pretty cool.

The sisterhood of Karn theory is also a cool one and I'd like to see them revisited in another webisode.

I'm sure Moffat will surprise us with something!