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.
While investigating a murder at a Quantico reunion, the NCIS team uncovers a bomb plot and a long-running theft ring; Torres and Quinn adapt to their new lives on Gibbs' team.
When a Marine falls to her death, the woman's doctor (Laura San Giacomo) tells Gibbs that she thinks the woman was murdered.
The body of a navy lieutenant is discovered aboard a destroyer while civilian guests are allowed to spend the night on the ship; McGee considers the perfect proposal for Delilah.
When a missing M16 officer is linked to the death of a petty officer, Gibbs sends Quinn and Bishop to investigate; Quinn recounts a painful ordeal that caused her to leave field work.
When a kidnapped officer escapes her captor, the team discovers a strange connection to her missing husband; Abby knits gifts for the new members of NCIS.
Torres breaks protocol when he learns that a witness in an NCIS case is wanted by U.S. Immigration and Customs Enforcement; Abby, Bishop and McGee try to woo Tony DiNozzo Sr. to sublet Tony's old apartment.
Agent Bishop questions her previous work at the NSA after being sent to Gitmo to gather evidence for a Navy chaplain murder case; Bishop's brothers visit for Thanksgiving.
The team looks into a series of threats against congresswoman Jenna Flemming; Director Vance takes charge of temporary protection detail.
Evidence from the murder of a Navy captain leads the NCIS team to Ducky's deceased mother; the team exchanges holiday gifts; Gibbs has Christmas dinner with Fornell.
An operation to catch a businessman who is using acts of terror to manipulate the stock market is compromised, forcing the NCIS team to search for new leads.
When Gibbs identifies the brother of an NCIS most-wanted suspect, he goes under cover to penetrate their anti-government militia; Bishop and Reeves team up for a clandestine investigation.
During an NCIS hit-and-run investigation, Palmer joins a stranger on the outside ledge of a building in an attempt to save his life.
The murder of a petty officer in a small town outside D.C. prompts NCIS to once again work with The Sherlocks, a privately funded investigative team.
Abby is found in possession of a real bomb after her homeland security think tank is compromised; a theoretical terror playbook is stolen and is being auctioned on the black market.
Bishop is determined to get revenge for the murder of her late boyfriend, Qasim, after Gibbs and the team find a new lead in the Chen case; Torres teaches the agents the art of pickpocketing.
McGee finds his apartment torn apart by a robber trying to locate a valuable item hidden there by the convicted criminal who previously owned the unit; Congresswoman Flemming encourages Vance to pursue a career in politics.
To carry out a sailor's dying wish, Gibbs and the NCIS team re-investigate a murder case that was originally ruled an accidental death.
When a Marine is murdered at a charitable event, an irritable war veteran must help solve the crime; McGee and Bishop investigate an intriguing rumor about Quinn and Torres.
A ransom-seeking hacker infiltrates a vice admiral's laptop and threatens to erase his personal and professional files; Alex takes time off to assist her mother.
Torres turns to old case notes and contacts after a Marine's murder becomes linked to a former dirt bike gang he joined for a year-long undercover operation.
After a Marine sergeant is found murdered in a national park, Gibbs and the NCIS team partner with May Dawson, a mounted police sergeant, to solve a string of related crimes in the park.
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.