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.

The team is surprised when Gibbs asks Tony's father to join them in a murder investigation.

After Anthony DiNozzo, Sr. is found in a car with a dead body in the trunk and no memory of the previous night, the NCIS team must figure out if he is capable of murder. Meanwhile, Tony is sidelined for this case and must go against orders to try and prove his father’s innocence.

Someone winds up dead when DiNozzo confronts a man impersonating a Navy officer; DiNozzo's father needs to share a secret with his son.

Evidence in an NCIS murder case reveals a rare painting on loan had been swapped for a fake, prompting DiNozzo, Sr. to share his knowledge and contacts of the black market art world with the team.

DiNozzo is partnered with his girlfriend ATF Special Agent Zoé Keates after evidence reveals that the murder weapon in an NCIS case was originally purchased for the controversial ATF sting operation “Operation Fast and Furious.” Also, Anthony DiNozzo Sr. returns to town for a special dinner to meet his son’s girlfriend.

A Navy Public Affairs officer is murdered, and the victim's wife and mistress accuse each other of the crime. Meanwhile, Anthony DiNozzo Sr. helps a homeless woman who believes he is her father.

NCIS, FBI and MI6 continue an international manhunt for an escaped British spy who is targeting current and former agents.

Torres boldly breaks protocol when he learns a witness in an NCIS case is wanted by U.S. Immigration and Customs Enforcement. Also, Abby, Bishop and McGee woo landlord Tony DiNozzo Sr. in the hope of subletting Tony’s apartment.

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 that includes their newest member, Anthony DiNozzo, Sr.

The NCIS headquarters are evacuated after the team discovers a body as well as bomb materials on the roof of the squad room. Also, the team reads the first draft of Ducky’s book.

Jimmy is torn between family and work after his father-in-law, Ed, asks him to tamper with evidence from NCIS’ current murder investigation. Also, Ed’s poker buddy, Anthony DiNozzo, Sr., offers to help with the case.