The character of Henrietta "Hetty" Lange did not leave the show "NCIS: Los Angeles" and is still part of the show's 2015 to 2016 season. There was a storyline during the season 3 finale of the show where Lange resigned her position as the operations manager and supervisor of the NCIS team. While she was replaced by the character of Assistant Director Granger in the season finale, Lange returned for season 4 of the show.
NCIS stands for Naval Criminal Investigative Service and actress Linda Hunt has played the character of Lange since 2009. "NCIS: Los Angeles" airs on CBS and was the fifth-highest rating show on the network, as of 2015.