Claire Danes, Mandy Patinktin, Laila Robins and Michael O'Keefe all play main characters in the fourth season of Homeland. While Danes and Patinktin were part of the cast since it originally aired in 2011, Robins' and O'Keefe's characters were introduced around the beginning of the fourth season.
The fourth season aired in 2014 on the Showtime channel. The season started with Danes' character, Carrie, working as the CIA station chief in Kabul, Afghanistan. Throughout the season, Robins' and O'Keefe's roles became intertwined with the original cast.
In the original "Homeland" script, Carrie's name was written as Claire. It was changed to Carrie after Claire Danes accepted the role.