The team investigates a car explosion with a connection to an agent who went missing six months earlier; Gibbs asks NCIS Special Agent Alex Quinn to shadow his team.
A marine sergeant falls from a building, it appears she attempted suicide, but her psychiatrist, Dr Grace Confalone, urges Gibbs to investigate her attempted murder.
Gibbs sends Bishop and Quinn to Philadelphia to work with MI-6 Officer Clayton Reeves on the murder case of a British operative. Meanwhile, Quinn deals with the NCIS case that caused her to leave the field.
Torres breaks protocol when he identifies a suspect that is wanted by ICE; Abby, McGee, and Bishop try to woo Anthony DiNozzo, Sr. Into subletting his son's apartment.
Bishop questions her previous work at the NSA when she's sent to Gitmo to collect evidence for a Navy chaplain murder case. In the meantime, her brothers visit for Thanksgiving and want to know from her co-workers who she's dating.
The team searches for new leads when an undercover mission to apprehend a businessman who's committing acts of terrorism to manipulate the stock market is compromised.
Bishop is more determined to avenge her boyfriend's murder when the team finds a new lead in the Chen case. In the meantime, Torres teaches his fellow agents the art of pick-pocketing.
The stress of McGee and Delilah's upcoming wedding lands Delilah in the hospital; the NCIS team investigates the mysterious death of a healthy, young petty officer aboard a Navy destroyer.
Gibbs, McGee and Torres travel to a remote area of Paraguay, controlled by a violent group of rebels, in an attempt to locate a missing Navy Seal who disappeared during an unsanctioned trip.