"The roads have demons beneath," we're told in the new trailer for "Sherlock's" fourth season, "and yours have been waiting for a very long time."

It's a grim warning for the world's greatest detective, paired with images of Benedict Cumberbatch as a distraught Sherlock Holmes and Toby Jones as a truly sinister, yet still unnamed, villain. "What is the very worst thing you can do to your very best friends?" the latter asks rather ominously as we're shown shots of Rupert Graves as Lestrade, Martin Freeman as Watson, Una Stubbs as Mrs. Hudson and Amanda Abbington as Mary. "Tell them your darkest secret."

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Debuting Jan. 1, the fourth season of the acclaimed drama picks up following the death of Season Three villain Magnussen and the apparent return of James Moriarty, as John and Mary prepare for their biggest challenge yet: parenthood. Although that description sounds cheery enough, the trailer makes it clear there may be more tears than laughter in the new episodes.

BBC Worldwide North America and Fathom Events announced Friday the Season Four finale will receive limited theatrical release in the United States on Jan. 16 and Jan. 18. The screenings will include 15 minutes of exclusive extras. For tickets, and for a list of theater, visit the Fathom Events website.

"Sherlock" Season Four premieres Jan. 1 on BBC One in the United Kingdom and PBS in the United States.