A Marine famous for pulling his original pranks is found murdered on the night of Halloween and the NCIS team uncovers that the victim's pranks may have become a ghoulish retribution.
Nielsen Ratings: Code of Conduct was seen by 21.25 million people, and was rated 13.0/21 in households, 6.5/17 in adults 25-54, and 4.7/13 in adults 18-49. This episode delivers the show's best household ever, matches the best adults 25-54 performance, and for the third conscutive week, it was the show's second largest audience ever.