Beckett is recruited to assist on a Narcotics investigation, but a routine mission turns deadly when an undercover operation goes array. To survive, Beckett must engage in a battle of wits against some of the most dangerous men in the New York underworld—including a powerful enemy from her past.

Castle and Beckett investigate the murder of a Wall Street trader, but the case takes a shocking turn when the they discover the victim was an undercover informant for the U.S. Attorney's office. To complicate matters further, the U.S. attorney involved is Elizabeth Weston, Captain Gates' estranged sister.