(EW.com) -- "Downton Abbey" is getting another American visitor.
"Sideways'" star Paul Giamatti will appear as Cora's playboy brother, Harold, in the season four finale, a rep for Masterpiece on PBS confirms.
He'll be joined by returning guest star Shirley MacLaine, who crossed the pond to play Cora's brazen mother, Martha Levinson, in season three.
"We're excited that Paul Giamatti will be joining us on 'Downton' to play Cora's brother Harold, the rather free-spirited uncle to Mary and Edith. We can't wait to see him work alongside Shirley MacLaine, who are both sure to upset the Grantham's apple cart in this year's finale," executive producer Gareth Neame said in a statement.
Giamatti is hardly the only new face joining the series — next season will introduce a slew of castmembers, including Dame Kiri Te Kanawa, Tom Cullen, Julian Ovenden, Nigel Harman, Joanna David and Gary Carr.
Season four of the series will kick-off on January 5, 2014.
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