Fans have waited a long time for the fourth season of Sherlock to premiere. The third season ended on January 12, 2014 and only a single episode has aired since then, 'The Abominable Bride' around Christmas of 2015. The wait finally ended on New Year's Day, 2017 with 'The Six Thatchers', written by Sherlock executive producers/creators Mark Gatiss and Steven Moffat and directed by Rachel Talalay (Doctor Who).
Sherlock tells the familiar story of Sherlock Holmes and his best friend John Watson, with a twist. The famous literary characters are played by Benedict Cumberbatch (Doctor Strange) and Martin Freeman (The Hobbit). Set in modern times, the "consulting detective" and his partner use blogs and Google to aid them in their crime-solving. The show also emphasizes the worst aspects of Sherlock's character, such as his drug use and anti-social behavior, traits often de-emphasized in previous adaptations. At the heart of Sherlock is not the murder and mysteries but the friendship between these two grown men, carried by the stellar performances of both actors behind them.
According to overnight ratings (as reported by Deadline), 8.1 million people tuned in to watch the Sherlock season 4 premiere on New Year's Day, making it the most watched show of the entire day. However, that is a small drop from last year's Sherlock special 'The Abominable Bride', which had 300K more viewers than that, and it is down a significant 1.1 million viewers from the show's season 3 opener's ratings, 'The Empty Hearse'.
There could be a few reasons for this rating drop. One theory is that the wait was too long, and viewers may have moved on. Three years with only one episode in the middle is quite a bit of time between seasons. Another possibility is the cliffhanger. Season one ended with Sherlock seemingly ready to blow up himself and Watson in order to stop Moriarty, and season two ended with audiences wondering just how Sherlock managed to survive his terrible fall that made everyone think he was dead. Season three ended on a strong cliffhanger as well, a message from Moriarty which came from beyond the grave to taunt Sherlock. But that ending was partially dealt with in 'The Abominable Bride' so there was not quite as much urgency surrounding it.
It could also simply be that more people had plans for the New Year and recorded the Sherlock season 4 on their DVRs, in order to watch it later. The ratings for the remaining episodes of the show's fourth season may shed more light on that matter and better illustrate whether the series appears to have diminished in popularity slightly - or is still going as strong (stronger?) than ever.
The fourth season of Sherlock continues on PBS with 'The Lying Detective' airing on January 8 and the final episode of the season, 'The Final Problem' airs on January 15.