Lee Wuan Kai was a North Korean assassin who was responsible for the death of Leon Vance's partner, Neil Wilson nearly 20 years ago, causing Vance to develop a strong obsession with capturing or killing her once and for all.
From early childhood, Lee (the first name in Korea is the family name) was trained, brainwashed, and manipulated into becoming an assassin for North Korea and as a result of the training, while unfortunately robbed her of her childhood, she became one of the world's very effective and deadly assassins.
Vance encountered Lee several times: first in Prague in 1984 where she killed his partner, Neil Wilson, then in Tokyo in 1991; and then in Sierre Leone, Paris and New York City before finding her again in Los Angeles while he was assisting the Office of Special Projects with an investigation into the death of Daniel Su.
Lee and Vance met and exchanged gunfire after talking beforehand. Kai was wounded, but managed to escape. After this she hijacked a man named Jason Cutler while he was traveling around the country and had him fly back home, after which she killed him. Vance shot her in the chest and Lee was said to have gotten right up as if nothing happened.
Soon after, a doctor was found dead in Washington, D.C., and Vance identified the killer as Lee due to the way he was killed. This as such, led Leroy Jethro Gibbs's team to investigate the murder, seeking corroborating evidence. Lee would however kill again and it was soon discovered that she was killing the men who turned her into a killer. Kai then saved McGee's life when an assassin hired to find Kai threatened him at gunpoint where Kai shot and killed her. When they had enough to prove that Lee was the killer, they went looking for her. However, when Vance went home, Lee was there holding a gun on his wife Jackie. Lee asked Vance to kill her, as she no longer wanted to be an assassin and there was no other way out for her -- if she had simply quit, she would have been hunted down and killed by other North Korean assassins. Lee was then shot dead from behind by Jackie.
Having been brainwashed into becoming an assassin since she was very young, Lee is incapable of feeling any mercy, guilt or even love and is also unable to form any relationships with anyone in sight. She is a cold-blooded killer who will go to the extreme lengths to carry out a task and has no regrets over the crimes she has committed or the lives she has ruined or taken in her stead.
She however appears to change after her near-death experience and proceeds to get revenge on the men who did this to her and even saved a NCIS agent's life. Also when infiltrating Vance's house she incapacitates, not kills, the agents guarding Jackie and even waits for Vance's children to leave before making her move.
Kai was skilled in firearms and could use anything from a simple handgun to a sniper rifle. She was also capable of firing a single round from a gun, one that was capable of killing her target instantly.
- Neil Wilson.
- Twenty-seven contract kills.
- Daniel Su- (shot with sniper rifle).
- Jason Cutler- (hitched a ride while he was traveling across the country and then killed him).
- Elan Cirreux- (shot twice in the back after healing her, presumably at gunpoint).
- Pak Su Ji- (shot with sniper rifle and later died of poisoning which was revealed to have come from a bullet).
- Amanda Barrow- (shot from a distance, saving McGee's life).