With New Orleans decorated for Halloween, the NCIS team investigates the murder of a Naval Staff Judge Advocate found in a cemetery dressed in a Victorian costume with vampiric puncture wounds on her neck. Meanwhile, the team debates what Halloween night activity and costumes would be best.

The NCIS team investigates the murder of a Petty Officer found in a Mardi Gras float storage facility with an engagement ring and proposal plan in hand. However, the case takes a mysterious turn when the team is unable to locate his supposed long-term girlfriend.