Fans are thrilled to find out that after a year, make that two years actually, a new season of “Sherlock” is finally going to be aired. There has been no definite news or update regarding the said series until recently the network suddenly dropped the first official teaser earlier. Now, it has unleashed a longer trailer that previews what the new season is going to be all about.

After series creator, Steven Moffat confirmed in 2014 that the fourth season is in the works, it has also been revealed that the said upcoming season will run three episodes. The filming for the said installment began in April 2016 and lasted up until August 2016. Moffat has further revealed that the latest installment to the series is the darkest season yet.

Based on the recent trailer, it seemed like Moffat was not calling a bluff. Just on Dec. 10, the latest preview for “Sherlock” Season 4 was released stating that the new installment is not about a game anymore. The preview showed Doctor John Watson, portrayed by Martin Freeman, talking to Sherlock Holmes, played by Benedict Cumberbatch, about inner demons coming out in the open.

The trailer further revealed lines such as “What’s the very worst thing you can do to your very best friends? Tell them your darkest secret.” that clearly signifies the theme of “Sherlock” Season 4. The show introduced Toby Jones as a guest star who will play the role of the villain, Culverton Smith, in the series. Fans are also curious as to who exactly was Holmes was declaring his love to.

With the series exploring the main character’s past, Cumberbatch himself has actually suggested that this might just be the last season as it felt like the end of an era for him. The three upcoming episodes have already been titled as “The Six Thatchers”, “The Lying Detective”, and “The Final Problem”. “Sherlock” Season 4 will premiere on Jan. 1, 2017 on BBC for the United Kingdom and on BPS for the United States. The series will air until Jan.15 next year.