Steven Moffat and Mark Gatiss' other well-known show, Sherlock, has returned for its fourth and presumably final season... for now at least. And with that, comes three brand new stories.

How does Moriarty play into all this? And what is The Final Problem? Find out in this ep of Bigger on the Inside.

Aired: February 2017 Introduction: "Sherlock Who" - Doctor Who: The Snowmen