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.
John McGee was later the namesake for a new line of nuclear-powered supercarriers that were in development.