Sherlock teased the premiere of its fourth season with this trailer at San Diego Comic-Con, promising heavier action in the present-day take on Sir Arthur Conan Doyle's fabled consulting detective.
In the trailer we see a story arc that is darker and more violent than the preceding three seasons. The program's last full season came in 2014, though the BBC did air a one-time special episode at the beginning of the year. The hiatus has been partly attributable to the schedule of Doctor Strange's Benedict Cumberbatch, who plays the lead role.
This season kicks off with an episode directed by Rachel Talalay, well known for her work with the BBC's Doctor Who series. The fourth season will be co-written by Steven Moffat and Mark Gatis. Though both appeared at a Comic-Con panel to discuss Sherlock's return, neither could say if a new season or if this is the last.