NCIS: Season 7, Episode 20

7 - 20: Moonlighting

When the NCIS team finds a dead Navy petty officer and FBI informant, they call in Agent Fornell to assist with the investigation. Fornell reveals that a string of similar security leaks have been occurring, and they trace the source to a private security company. They also discover that their NCIS polygraph specialist, Susan Grady, works part time at the same company. After retrieving her, the security company's office is destroyed in an explosion and Susan reveals that she stole some polygraph data for personal use. Abby manages to deduce that the killers inadvertently killed themselves in the explosion, leading Gibbs and Fornell to the real mastermind: a federal judge they both had interviewed during the investigation. She went on a secret crusade to kill informants who would take reduced sentences in return for their testimony, and wanted to destroy the polygraph data as it might implicate her involvement.