The much-liked detective show, Sherlock, returned for its fourth season on January 1. The first episode, "The Six Thatchers," reached 3.7 million viewers in the US on PBS, according to Deadline, which is down slightly from Season 3's January 2014 premiere of 4 million.That number was a record for the Benedict Cumberbatch-starring show stateside.Compared to Sherlock's January 1, 2016 special, "The Abominable Bride," Season 4's premiere rose 7 percent in viewership on PBS.In the UK, Sherlock's Season 4 premiere tallied more viewers.