As fans reel from the ending of another "Downton Abbey" season, ITV and Carnival Films, the show's producers, have announced some details about the upcoming Christmas special, which will be released on Christmas day in the U.K. The popular British costume drama will not air in the U.S. until January.

In a press release, ITV announced the cast for the Christmas special and gave some details as to what would happen in the two-hour special. The Crawleys have been invited by the Sinderbys to Brancaster Castle in Northumberland for grouse shooting season.

Joining the cast as special guests is Alun Armstrong, who will play Stowell, Sinderby's butler. Jane Lapotaire will play the elusive Princess Irina, which means we will finally meet Prince Kuragin's missing wife. What will this mean for the Dowager Countess?

While the family enjoys the shoot, ITV says Stowell will threaten the fun with a "scandalous secret." Back in Downton, the servants are going through their own lives. Bates hatches a drastic plan to free his wife from prison while Carson and Mrs. Hughes join forces in a new business venture, hinted at during the season.

The Christmas was filmed at Alwick Castle in Northumberland for two weeks. Aside from the original cast, James Faulkner, Penny Downie and Matt Barber return as the Sinderbys. Rade Sherbedgia will return as Prince Kuragin and Michael Fox as the new footman, Andy.

According to Radio Times, Hugh Bonneville, who plays the family's patriarch, Lord Grantham, made the decision to kill off the family's golden labrador Isis. The actor rejected claims that the decision was based on the current situation in Iraq and Syria.

"Anyone who genuinely believes the Series 5 storyline (1924) involving the animal was a reaction to recent world news is a complete berk," he said.

"I suggested the storyline to Julian about a year ago," explained Bonneville, saying the dog was getting old. Julian Fellowes, the show's creator and writer, said he would consider it and then Isis passed during season 5.