The team search for a international serial killer who targets naval personnel and leaves a chilling calling card.
Seaman Derek Balfour is murdered in an alley but when his body is discovered days later it has been meticulously cleaned. When the team visit his apartment for clues, they find it spotlessly clean and empty, except for a flower frozen inside an ice cube in the freezer. The caretaker of the building informs them that someone other than Balfour has been staying there for the last four days.
Gibbs's is unhappy when Special Agent EJ Barrett arrives to take over the case. She explains that Balfour's murder matches several others she has been investigating, down to the flower in the ice cube. The other victims were all naval personnel and the killings are world-wide, from Guam, to Spain and Japan. Barrett's profile of the killer suggests they are well-off, well-travelled and medically trained and this leads them to a number of suspects...
The NCIS team are called to the Pentagon to catch a killer.