Only an episode is left before "Downton Abbey" finally bid its last goodbye.

After the last episode for season 6 was aired in the U.K. earlier this year, the critically acclaimed period drama will air a Christmas special that promises to be highly emotional. PBS recently released the promo trailer that seems to reveal a major tear-jerking episode.

Based on the trailer, the characters are starting to say their sad goodbyes in the midst of celebrating the holidays.

The conniving under-butler Thomas Barrow (Rob James-Collier) is seen saying goodbye to his job at Downton Abbey. In the video, the members of the estate staff, including George (Oliver Barker), look sad to see him go and even ask him to stay. "I arrived as a boy. I leave as a man," Barrow says in the trailer.

The special Christmas episode of "Downton Abbey" season 6 also features a scene during the Crawley estate's New Year's Eve celebration. The trailer shows Mr. Carson (Jim Carter), one of the people reluctant to accept that times are changing, will finally settle for the changes coming. "The world is a different place from the way it was, my lord. And Downton Abbey must change with it."

But perhaps the most heart-rending scene in the trailer features Dowager Countess (Maggie Smith), who explains to Isobel (Penelope Wilton) why she enjoys celebrating New Year's. "Makes me smile," Dowager Countess Violet says. "Every year, we drink to the future, whatever it may bring."

Tom Branson (Allen Leech) also appears in the promo trailer for the final Christmas special of the series, while Lady Rose (Lily James) is also seen kissing her husband at the end of the video.

British fans of "Downton Abbey" can enjoy the final episode of the series on ITV on Dec. 25, while U.S. viewers will only see the premiere episode of season 6 on Jan. 3, 2016.