The BBC has debuted a new trailer for the fourth season of "Sherlock" that teases the return of Moriarty, a frightened Holmes, and a confrontation between Mrs. Hudson and Mycroft.

"Something's coming," Benedict Cumberbatch's Sherlock says. "Maybe it's Moriarty, maybe it's not." Whatever it is, it clearly has the world's greatest detective spooked yet as witty as ever.

Also starring Martin Freeman as John Watson, "Sherlock" returns in 2017.