EJ Barrett's team, on the trail of the Port-to-Port killer get news of the murder of an NCIS agent, Earl Stark. His body is in a forest and his throat cut by what may be a scalpel – in keeping with the Port-to-Port killer’s style.
Meanwhile Gibbs reviews the information that Barrett's team uncovered on their recent trip to Hawaii where the Port-to-Port killer claimed another victim at the Pearl Harbor Naval Base. A trip to the evidence locker and a reappraisal of several items gives Gibbs a strong hunch as to the identity of a key lead: CIA agent Trent Kort. He's been working on a parallel mission to catch the serial killer and he has a name for the suspect – Lieutenant Jonas Cobb.
The team discover Cobb took part in Operation Frankenstein: a top secret mission to place highly trained undercover assassins within the most secretive terrorist networks across the globe. With such a tricky target, Gibbs calls on help from his old friend and former mentor Mike Franks.
As the team chase every possible lead, Cobbs strikes another lethal blow to the heart of the agency...