Hollis Mann is an agent with the Department of Defense who is also a former member of the CID- Criminal Investigation Division and a former Lieutenant Colonel in the United States Army.
Born in an unknown State in America, Mann joined the United States and subsequently rose to the rank of Lieutenant Colonel with one of her previous postings including the 82nd Airborne Division.
She later joined the Army CID (Criminal Investigation Division).
NCIS Season 4
Mann first appeared in "Sandblast (episode)", where she was the head of the Army CID investigation into the bombing at the Army-Navy Club. Joining forces with Special Agent Jethro Gibbs, the two began tracking a terrorist with a personal expertise in explosives. The two displayed immediate chemistry, and Tony went so far as to call her "Gibbs' fourth ex-wife" in Season 11 "Kill Chain (episode)." They discovered the bomber to be Mamoun Sharif, whose final bombing was thwarted by the joint team, though Sharif escaped.
The hunt for Sharif would lead them to meet again in "Sharif Returns (episode)", after he stole a cache of chemical weapons from the military. Her relationship with Gibbs became more serious, and she saved his life after Sharif poisoned him. This would lead the two to consummate their relationship later that night.
NCIS Season 5
NCIS Season 11
Retired Lt. Colonel Hollis Mann returns again in "Kill Chain (episode)" and we find out that she has since married. When she shows up at the NCIS office, Director Vance asks Gibbs if she is another one of his ex-wives. Gibbs responds, "Might as well be."
NCIS Season 12
Mann is a tall woman in her mid-forties with shoulder-length blonde hair and green eyes.
Lt. Colonial Mann demonstrated that she has equal ability as Gibbs in managing the NCIS team.