Matt Barber, Atticus Aldridge, and Peter Egan will also return in the episode, where the residents of the house will ring in 1926 with a New Year’s Eve celebration.
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It won’t be all celebrating though: Mary struggles to reconcile with her sister, Edith tries to deal with the threat of her secret, and both Henry and Carson grapple with recent life changes.
The Downton Abbey finale will air Dec. 25 in the U.K. and May 6 on PBS in the U.S.