Mary Catherine McCormack (born February 8, 1969) is an American actress. She has had leading roles as Justine Appleton in the series Murder One (1995–97), as Deputy National Security Adviser Kate Harper in The West Wing (2004–06) and as Mary Shannon in In Plain Sight (2008–12).Her film roles include Private Parts (1997); Deep Impact (1998); True Crime (1999); High Heels and Low Lifes (2001); K-PAX (2001); Right at Your Door (2006), and 1408 (2007).