Melissa Chessington Leo (born September 14, 1960) is an American actress. After appearing on several television shows and films in the late '80s, her breakthrough role came in 1993 as Det. Sgt. Kay Howard on the television series Homicide: Life on the Street for the show's first five seasons from 1993 – 1997. She was also previously been a regular on the television shows All My Children and The Young Riders. Her breakthrough film role was in the 2003 film, 21 Grams as Marianne Jordan. She was also in the 2013 film Oblivion, starring as the main antagonist Sally.