CBS | 8:00 pm

While the NCIS team is involved in the pursuit of a deadly arms dealer, they're shocked when Bishop (Emily Wickersham) is implicated in an old NSA leak in the Season 18 finale, "Rule 91." Meanwhile, Gibbs and Marcie (Mark Harmon, guest star Pam Dawber) suddenly realize that the killer they've been tracking may be aware of their interest. Recurring guest star Katrina Law also is featured, along with Sean Murray and Wilmer Valderrama.