The people who inhabit the Downton estate have reasons for some cheer. This week's episode of "Downton Abbey" has relationships at its crux, and audiences will get to experience it in its varied forms.

The promo for episode 3 teases Lady Mary's (Michelle Dockery) love life, Mrs. Hughes (Phyllis Logan) wedding and Lady Edith's (Laura Carmichael) journey to London.

From the preview clip, we can tell you that the wedding we've been waiting for, the one that involves Downton Abbey's beloved butler, Mr. Carson and Mrs. Hughes, will finally take place in episode 3. Pictures released by Carnival Films revealed a radiant Mrs. Hughes in mauve gown standing alongside her proud husband, Mr. Carson (Jim Carter).

The rest of the staff and the members of the Crawley family attend the ceremony. Nevertheless, we are left to wonder where the reception will take place.

In the previous episode, Lady Mary suggested to Mr.Carson that they could hold the reception in the great hall of the estate but his fiancée, Mrs. Hughes, was opposed to the idea.

The other plotline that episode 3 will explore relates to Lady Mary's love life. In the promo clip, the eldest daughter of Lord Grantham receives a surprise visitor, one who is Lady Shackleton's nephew. Fans of the show will remember that Henry Talbot's (Matthew Goode) aunt also lives in Yorkshire.

And it's about time that Lady Mary exited from her long vacation in singledom.

"Downton Abbey" season 6, episode 3 will air on Sunday, 9pm on ITV. You can watch the episode online via ITV Player.

Watch the trailer here: