Ziva goes undercover to catch a dangerous serial killer preying on women living on a Navy base. Evidence mounts against a suspect, who becomes suspicious of Ziva. Exposed and with her life on the line, Ziva kills the suspect. The case is solved-until Ducky's autopsy on a victim reveals she was killed by someone else. As the team searches down the second murderer, Ziva strugles emotionally to deal with the work she has been trained to perform.