On the last episode of "Downton Abbey," the posh inhabitants hosted a lavish affair that involved a famous opera singer, new faces and a shocking incident. 

Downton hosts 16 guests for a long weekend of decadent dinners and a performance by famous opera singer Nellie Melba, who is played by real-life opera star Kiri Te Kanawa.

The influx of house guests means some of their valets and servants also came to the Abbey, including guest Lord Gillingham's (Tom Cullen) flirtatious valet who takes a shine to Anna (Joanne Froggatt), to the chagrin of Bates (Brendan Coyle).

Lord Gillingham (Tom Cullen) is an old family friend who makes an instant connection with Lady Mary (Michelle Dockery). For the first time since Matthew's (Dan Stevens) death, Mary cracks a smile while chatting with Gillingham. While she feels a bit guilty for feeling happy after her devastating loss, she welcomes his company, and recognizes his growing affection for her.

Isobel Crawley (Penelope Wilton), Matthew's mother, reluctantly attends the jovial event, and can't help feeling dejected during the merrymaking.

Meanwhile, Branson (Allen Leech) is feeling increasingly uncomfortable in Downton's social situations. He still feels like he doesn't belong with the upper-crust of British society, and still understands the downstairs staff better the wealthy partygoers upstairs. Scheming housemaid Edna Braithwaite (MyAnna Buring), who left Downton after having a fling with Branson, once again tries to win over his affections. 

Hapless Molesly (Kevin Doyle) also returns to Downton to be a footman as a stand-in for Jimmy (Ed Speelers), who injures his wrist while showing off for Ivy (Cara Theobold).

Michael Gregson (Charles Edwards) also attends the party as Edith's (Laura Carmichael) guest. While at first Lord Grantham (Hugh Bonneville) does not seem taken with Edith's new beau, he warms up to him after Gregson wins back money they lost to a house guest who was cheating at poker.

At episode's end, the opera singer belts out a gorgeous rendition of a Puccini tune. The entire house--the downstairs staff included--is invited to see the opera virtuoso sing. Anna has a bit of a headache, so she leaves the performance to go downstairs and take some medication.

While downstairs, she runs into Lord Gillingham's flirtatious servant, who won't let Anna pass to walk back upstairs. When Anna tries to get by him, he slaps her, then forcibly drags her to an empty room, where he violently forces himself on her.

After the opera singing is done, Mrs. Hughes (Phyllis Logan) goes downstairs to find Anna, beaten up, shaking and crying. Anna tells Mrs. Hughes not to tell anyone about the horrible ordeal, as Bates would most likely kill the perpetrator and end up back in jail.

On the next episode, "Love is in the air at Downton Abbey and darker emotions too, as Mary, Edith, Tom, and Anna each struggle with a dilemma. Things are cooking for Ivy and Alfred, and heating up in London."

Lord Gillingham will also show up at Downton again, and Anna will struggle with the aftermath of being sexually abused. 

Watch the promo for episode three below, which airs Sunday, Jan. 19 at 9 p.m. on PBS.