Toby Jones, Benedict Cumberbatch and Martin Freeman appear in new 'Sherlock' Season 4 trailer

LONDON, Dec. 11 (UPI) -- The BBC has released a second trailer for Season 4 of its beloved detective drama Sherlock.

Saturday's 45-second clip features the return of series regulars Benedict Cumberbatch as the titular sleuth, Martin Freeman as his close friend John Watson, Louise Brealey as his love interest Molly Hooper, Mark Gatiss as his brother Mycroft and Rupert Graves as his associate, Detective Inspector Lestrade.

Also making an appearance in the video is Toby Jones whose villain Culverton Smith joins the cast this season.

Here, Smith taunts Sherlock, asking: "What's the very worst thing you could do to your best friends? Tell them your darkest secret."

The show is to begin its next season on Jan. 1 on the BBC in the United Kingdom and on PBS in the United States.