NCIS Season 10Edit
Admiral McGee made his appearance in the Season 10 episode, Squall (episode) where there was clear some tension existed between himself and his son.
Later, during a talk with NCIS Director Leon Vance, Admiral McGee also expressed some disapproval towards his son's job, believing that being an NCIS Special Agent was actually a paper-pushing job despite Vance attempting to convince him otherwise.
It was later revealed that he had been diagnosed with a terminal form of cancer.
NCIS Season 12Edit
In the Season 12 episode, House Rules (episode), it was revealed that John McGee had eventually succumbed and died from the cancer.