When she was a deeply troubled teenager, Nikita was rescued from death row by a secret U.S. agency known only as Division, who trained her as a spy and assassin. Nikita was eventually betrayed by the only people she thought she could trust. Now, after three years in hiding, Nikita is seeking retribution and making it clear to her former boss, Percy and her former friends Michael and Birkhoff that she will stop at nothing to expose and destroy their covert operation. Division continues to recruit and train other young people, among them Jaden and Thom, erasing all evidence of their former lives and turning them into cold and efficient killers. One of these new recruits, Alex is a beautiful girl with a violent past and a story not so different from Nikita's. The recruits all spend part of their training with Amanda, a master manipulator who can turn any ugly duckling into a swan and any bleeding heart into a killer.

Percy and Michael take their latest assignment, a Slavic leader wanted for war crimes, into protective custody. Nikita learns of their hideout and attempts to thwart their plan, but a mysterious group of mercenaries in search of nuclear material beats her to the task. Alex is activated earlier than expected for a special assignment that throws her into the crossfire of bullets. A flashback reveals a pivotal moment in Nikita's life.

Owen leaks secret information from Division’s black boxes to the media, revealing that the U.S. Government was responsible for an assassination in Chile. As a result, Percy frames a C.I.A. agent, Ryan for the crime. Nikita and Owen go to Chile to rescue Ryan from mercenaries and in doing so end up getting captured. Nikita reveals the secrets of Division to Ryan in an effort to save all of their lives. Back inside Division, Alex spies on Percy and Birkhoff and witnesses a side to Percy she has never seen before.

Nikita and Michael plot to take down Division and Oversight and are prepared to use the contents of the black box to do so. Amanda is now running Division but Oversight has assigned one of their own, a new agent named Sean, to keep an eye on her. Amanda's first mission is to get back the black box from Nikita, and she enlists Alex's help to do so. Alex refuses until Amanda tells her she will help her find the man who killed Alex's father. Meanwhile, Nikita and Michael find help from an unlikely ally.

Percy calls the President the United States and threatens to set off a nuclear explosion unless his demands are met. Birkhoff finds two scientists who could help stop Percy’s new nuclear satellite, so Nikita and Michael head after one and Sean and Alex look for the other. Unfortunately, Alex and Sean get caught at the very location that Percy blows up as an example of his power. Meanwhile, Nikita realizes the best way to stop Percy is to go into the belly of the beast – Division itself.

When Ryan tells Nikita an undercover agent has been arrested and they need to extract her from prison, Nikita questions why Division is continuing to run Percy’s old missions. Nikita, Michael and Sean attempt to stop a terrorist attack but are one man down after Alex is shot. Meanwhile, Birkhoff and Sonia continue to bicker.