Downton Abbey: The Grand Finale will usher in the end of the long-running franchise when it is released in September. However, details concerning the cast of The Grand Finale suggest that Mary (Michelle Dockery), one of the most beloved characters in the series, may not get a very satisfying ending. This follows one of the saddest moments in Downton Abbey: A New Era, which saw some notable changes to the cast of the franchise. Crossing from a hit television series into a hit film series has been a challenging move for Downton Abbey, and there have been several difficult ramifications.