'Sherlock' season 4 release date, spoilers news 2016: Latest trailer teases dark secrets; finale coming to US cinemas

BBC has released a new trailer for season 4 of "Sherlock." The latest footage shows the titular protagonist, played by Benedict Cumberbatch, in a very dark place with the stakes much higher this time around.

"What's the very worst thing you can do to your very best friends? Tell them your darkest secret," villain Culverton Smith (Toby Jones) taunts Sherlock.

The clip ends with Sherlock saying, "I love you." But viewers will have to wait until New Year's Day to find out who he says it to.

The first installment in the three-episode season is titled "The Six Thatchers." It is based on Sir Arthur Conan Doyle's novel titled "The Adventure of the Six Napoleons." It will be followed by "The Lying Detective."

Meanwhile, it has been announced that the season 4 finale, titled "The Final Problem," will be airing in cinemas in the United States on Monday, Jan. 16, 2017, and Wednesday, Jan. 18, 2017 at 7 p.m. local time. The special event will be available in nearly 350 movie theaters and will feature 15 minutes of extras. Tickets can be purchased online at the FathomEvents website.

"We can't think of a better way to start the new year off then experiencing the adventures of Sherlock Holmes and Dr. John Watson on the big screen. The bonus content will be an excellent treat for the show's loyal fans," said Soumya Sriraman, executive vice president of franchise and digital enterprises for BBC Worldwide North America.

The cinematic airing of the season finale will definitely be a special event that die-hard fans won't want to miss considering that they may not get another offering of the series anytime soon.

"It feels like the end of an era, to be honest. It goes to a place where it will be pretty hard to follow on immediately," the actor previously told GQ UK, adding, "We've made something very complete as it is, so I think we'll just wait and see. The idea of never playing him again is really galling."

While Cumberbatch clarified that the show will not be ending after season 4, he did say that the cast and crew will focus on other commitments for the time being.

Season 4 of "Sherlock" will premiere on Jan. 1, 2017, on BBC and PBS.