In the US, you can watch it on PBS on January 19. You can also purchase and download episodes from Amazon or iTunes after they air, or pre-order the DVD set which will be released in February.

You can watch it on BBC iPlayer if you download an unblocker. I use Hola unblocker (google it), it's safe and it works :)

BBC iPlayer.

bbc iplayer

It starts in the USA 19th Jan.

I don't really want to search around myself to get viruses. So if any of you guys have a good link that would be awesome. Also i haven't seen anything related to this episode, please no spoilers!