Sherlock season 4 episode 2
Sherlock Holmes with John Watson in Sherlock season 4 episode 2 BBC

Sherlock season 4 returns with an all-new episode this Sunday, 8 January, 2017 at 9pmGMT on BBC One and will be available on PBS Network for the US audience. In episode 2, titled The Lying Detective, Sherlock will meet the new villain in the series and will try to mend his friendship with John Watson.

The official synopsis for the chapter reads as follows:

Sherlock faces perhaps the most chilling enemy of his long career: the powerful and seemingly unassailable Culverton Smith - a man with a very dark secret indeed.

Click here to watch the episode live stream on BBC One in the UK and you can watch it online by clicking here. For the US viewers, you can watch the episodes online on PBS by clicking here.

The premiere episode ended with Mary Watson dying after she took the bullet and saved Sherlock's life. John Watson, who saw his wife dying in his arms, blames Sherlock, as he swore to protect her, but failed to do so. Sherlock even received a video from Mary, where she asked the detective to "save John Watson."

Sherlock showrunner Steven Moffat explained Sherlock and Watson's relationship in the upcoming episode. He told Entertainment Weekly, "We take that rift head-on in the remainder of the [season]. We don't ignore it. We don't have John come back and say, "Well I've thought about it and it's all fine." If anything, the rift gets worse. We decided if we were doing this we're doing grief properly. We were doing the consequences properly. "

Moffat continued, "We tried to have people go through what they'd actually go through in this circumstance which, of course, is hellish. And as emotionally reticent as Sherlock Holmes is, it doesn't take a 12-year-old to figure out he's a profoundly emotional man. We don't skirt around it. We don't just get on with the story of the week — although there is a story of the week. There's a big villain to fight. But front and center are the consequence of Mary's death and Sherlock's culpability. He could have done better, it's his lifestyle that killed her in the end."