As the hunt for Ziva's replacement begins, Gibbs and his remaining team members must head back to work with the past still weighing heavily on their minds.
The team discovers the bizarre death of a Marine and his two friends may be linked to their past, but its Gibbs who ends up taking a trip down memory lane.
When a Marine known for his practical jokes is found dead on Halloween Eve, the NCIS team discovers that the victim's "good-natured" pranks may have inspired ghoulish retribution. Meanwhile, Ziva tries to adjust to her new role on the team.
A murder investigation prompts Gibbs and the team to play family counselor to his former mentor, Mike Franks, in the hopes of preventing a bloody international conflict.
The body of the son of a retired Colonel-turned-preacher is found and the team have their suspicions that he may be the victim of a hate crime. Meanwhile, Gibbs gets a holiday visit from his father.
When a Navy pilot is found dead under strange circumstances in a secluded area, the team finds themselves battling a no-nonsense attorney with a hidden agenda.
Gibbs is worried about Tony's ability to handle his job when Tony's father turns out to be linked to their newest investigation, an assassination attempt on a foreign prince.
While on the flight back from Paris, Tony and Ziva realize that their assignment to protect a government witness in an embezzlement case is in great danger when they learn that an assassin is located on the same flight.
The team discovers striking similarities between themselves and their CGIS (Coast Guard Investigative Services) counterparts when a Navy diver seeking sunken treasure is found dead.
The death of a Navy officer leads Gibbs and the team into the world of high-priced call girls, relying on D.C. Madam Holly Snow to help them catch a killer.