Homeland and Pearson vet Morgan Spector will also join Downton Abbey creator Julian Fellowes' new drama set in 1880s New York. Baranski will play Agnes van Rhijn, "a proud and stubborn aristocrat who will never accept the world has changed and old values are being replaced by new ones." Sex and the City alum Nixon is returning to HBO as Ada Brook, the sister of Baranski's character, who is forced back on her sister's charity. Togetherness alum Peet is also returning to HBO. Peet and Spector will play a married couple. Spector's character is a classic robber baron of his time.