Xander Berkeley as Colonel Foster
Jonathan Foster, the charismatic leader of the Spearhead facility searching for a cure to the plague, is played by Xander Berkeley, another alumni of Nikita.
Alexander Harper Berkeley is an American actor. He is known for his television roles of George Mason on the political thriller series 24, Percy Rose on the action thriller series Nikita and Sheriff Thomas McAllister on the crime drama The Mentalist. He currently plays Gregory in AMC’s The Walking Dead.
In 2010, he received one of his best known roles – that of Percy Rose in the CW action-thriller series Nikita. He portrayed the character as a series regular in the show’s first two seasons as well as being the series’ de facto main antagonist of its first two seasons. Berkeley was Sheriff Thomas “Red John” McAllister on The Mentalist.
Berkeley portrays Gregory on AMC’s The Walking Dead, originally in a guest role in season 6, but was promoted as a series regular for season 7.
biography source: wikipedia