With prospering careers and a three year-old daughter, David and Tarilyn Deville seem to be living the American Dream. But instead of a life of comfort, tragic events in their past led the couple to a life of service - in the ER and District Attorney's office by day, and on the streets of Philadelphia by night as crime-fighters Midknight and Knightingale. Or, at least, after bedtime. But when they take a rare night out, their personal time is interrupted as the citizens of Philadelphia begin to tear the city apart!