MY THEORY

[goldvermilion87]

And I will not theorize any more from this day forward until 2016 when Sherlock Series 4 happens:

[This is to do with the end of His Last Vow. DO NOT CLICK UNLESS YOU'VE SEEN IT!]The villain who just popped up is the third Holmes brother that Mycroft mentioned.  The end.

Comments

[kizzia]

I concur. That would be lovely :)
Or possibly Moriarty's brother?

[rj_anderson]

This is my theory as well. The older, elusive Holmes brother's name is Sherrinford, for the record -- since they've already tapped into William S. Baring-Gould's The Private Life of Sherlock Holmes for Sherlock's "real" name and the existence of a third brother, I'll be surprised if they don't keep that detail as well.

I suspect that Sherlock does not know about the existence of this brother, however. He was older than Mycroft and somehow "died" or was packed off to somewhere remote to become The Thing That We Don't Talk About, so only Mycroft knows...

[goldvermilion87]

I'm also wondering if this is a bastard child of one parent, as they being reconciled would add more power to Sherlock making them an example for John and Mary.

[rj_anderson]

That's a possibility as well...

[sabrinaphynn]

It is a good, solid theory.

[rojo3131]

I love you for that theory