NCIS: The Penelope Papers

US Navy lieutenant Paul Booth is shot dead while sitting on a park bench. It turns out that the last people he called were his boss, his wife and Penelope Langston - a rebellious academic who also happens to be McGee's grandmother. She says that the victim was an old student of hers who kept in touch, but later reveals she was recruited to work on a special project during the Vietnam War by the head of a top-secret think tank Booth was a member of. Guest starring Lily Tomlin, with Mark Harmon and Sean Murray