A sailor is murdered and the Agents quickly locate the 'suspect' and bring her back to the crime scene for identification. The Agents watch in horror as Ducky is stabbed at a crime scene - and they uncover a secret from Ducky's past that led to the attack.
The team finds some numbers written in blood at crime scene. Gibbs instantly identifies the numbers as his, and knows it's a message for him. While the team tries to solve the murder, Gibbs calls his mentor Mike Franks in for help.
A murder with a connection to an old case leads to a reversal of roles for Gibbs and DiNozzo. DiNozzo leads the team in the investigation linking the murder to an embezzlement scheme that sent an innocent man to prison.
A blogger with a rep for exposing cover ups is murdered. His last blog involved a bungled NCIS investigation. The team investigates as best they can, while Metro PD investigates the blogger's NCIS claims.
Ducky suspects everything was staged, with forensic expertise, when retired NCIS agent Mike Franks's boat, still registered in donor Gibbs's name, hits a Navy ship, carrying the corpses of dishonorably discharged crooks Roy Keenan, US Army, and US Navy lieutenant Calvin Thomas Blanchard. They asked for Franks at his Mexican home, but no connections between them and Franks are known. The two met when in retired Colonel Merton Bell's PMC ('private military company'), the largest in Iraq. Franks turns up as well as his family's Iraqi matriarch.
A North Korean assassin, who is a nemesis of Vance's, resurfaces not long after a confrontation with him in Los Angeles. Now she is after his family and the key to saving them is to dig through Vance's troubled past.
Kids illegally hacking a Christmas tree find USMC lieutenant Thom Ellis, frozen and skull smashed bizarrely, on a Muslim prayer mat. Although his father, retired marines colonel George Ellis, became a protestant reverend, Thom converted to Islam during the Iraq war. That caused serious tension in his unit and his family, which includes younger brother Pat and widow Tina, who had an adulterous affair. Someone arranged for Roughnecks to get violent. Meanwhile Ducky helps Gibbs find out why his dad really visits 'for Christmas', Tony and McGee have a hard time doing ...