As NCIS mourns the loss of Ducky, the agents find comfort in working on one of his unfinished cases involving a woman whose father was dishonorably discharged from the Marines.
The NCIS, FBI and MI6 teams continue the international manhunt for an escaped British spy who's targeting current and former agents. Anthony DiNozzo bids farewell to NCIS.
Having not heard anything from Ziva, Gibbs, Tony, McGee, and Abby wonder; each starts sniffing and digging; they trace her to Somalia. Gibbs, Tony, and McGee go there; Tony and McGee become caught; Gibbs springs them all; they all go home.
After a malnourished and confused 9-year-old is found hiding in a storage unit, the team reopens an old missing persons case that Special Agent Ziva David had a personal interest in.
While investigating an off-base burglary at an Admiral's residence, NCIS becomes involved in a case of an older man that claims to be a Pearl Harbor survivor. He wishes to have his remains buried on the USS Arizona.
NCIS comes under attack by a mysterious enemy from the past. Vance tries to mend fences with his estranged son by explaining why, despite the ongoing dangers of his job, he still chooses to stay at NCIS.
Tony opens a letter, literally SWAK, dispersing a fine white powder; the gang does the drill. Kate and Tony get a free trip to Bethesda. Gibbs and company find both the bad lady and the solution of a two-year-old rape case at the USNA.
An ambush in an alley behind a bar leaves one Marine dead and one very ill; the gang investigate. The survivor is from Gibbs's hometown, and the team goes there; flashbacks abound. The bunch put the pieces together and nail the bad guys.