On a humid summer night in New York, a woman is gunned down in front of the diner she owns with her husband -- but is it a random act of violence, or a premeditated murder?

For homicide detectives Lennie Briscoe and Ed Green, what starts as a simple investigation soon becomes an increasingly complicated case of government secrets, international espionage, and hi-tech surveillance. Their greatest surprise, though, comes when the trail of clues leads them to the New York offices of the FBI!

Is the Bureau hiding a killer -- and if so, is there anything that prosecutors Jack McCoy and Serena Southerlyn can do to bring him to trial? Or will a murderer have to walk, in the interests of national security?