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.
NCIS Special Agent in Charge Feng Zhao, Knight's father helps the team unravel the mystery of a recently used service weapon belonging to a missing agent. McGee is in a tailspin when DNA results reveal a close relative he was unaware of.
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.
Three bodies are found on an old Navy ship that's about to be sunk and turned into an artificial reef. When Parker and Knight are going to investigate, they're suddenly locked inside by a mysterious figure.
