Glass Curtain is a high-tech terrorist organization that attracts new members via internet chat rooms. Posing as a new recruit, Nikita is taken to Glass Curtain headquarters, where she discovers that Michael's wife Simone is being held hostage. A former Section One operative, Simone was believed killed years before. Now, Michael's continued love for Simone may threaten the success of Section One's attempted infiltration of Glass Curtain.

When an international arms smuggler steals a canister of deadly nerve gas, Nikita and Michael pose as a married mercenary couple in order to infiltrate his compound. However, when the gas is discovered wired to a bomb in a crowded train station, Nikita must put her life on the line to defuse it.

The CIA believes that a rogue element of their agency is responsible for a recent massacre of heroin dealers, performed in order to steal money and drugs as part of an embezzlement scheme. Section One is brought in to clean the house quietly, but Nikita's continued involvement with architect Gray Wellman is tampering her ability to be a reliable operative. As Section One's operation reaches a fever pitch, Nikita is unable to balance both sides of her life, and is forced to make a choice between the organization that controls her life and the one man that she's ever loved.

A live nuclear warhead is smuggled into the states and the only witness to the act is a mentally challenged pizza driver named Rudy who witnessed the transfer. A transmission claiming that the warhead is armed in a random city and will detonate in 24 hours is intercepted and Section uses Rudy to determine who the man is that brought the warhead into the country - a traitor in the Agency. The location is discovered and with Rudy's help, Birkoff is able to determine the code that will disarm the bomb in time. Rudy is allowed to live due to his help and is allowed to leave Section with Nikita's assurances that he will never tell anyone of Section or it's whereabouts.

Section was informed that the water of the city would be polluted if the United Coalitions needs weren't met. Gregor Kessler, the one with many aliases and disguises, steals the Cobalt 60. Kessler was offered money to get the Cobalt 60, reported by a spy of Section. Gregor dresses up as an aged lady to get through South American Customs. Kessler manages to capture the Cobalt 60, but Madeline confronts him. Some how, he knows about her past and starts intimidating her. Section takes Kessler's daughter in hope to retreive the Cobalt 60. This doesn't work for him because he kills her, so Section can't hurt her. Meanwhile, Nikita finds out more about Madeline's past & what she did to her sister. Madeline never wanted anyone to know about it. Kessler now wants Madeline, Section doesn't want her to go by herself, so they stand by in a nearby distance. Madeline falls into a hole where Gregor is. He grips her up by the neck, but she breaks free. It wasn't really her, it was Michael dressed up

Section One is hot on the trail of Tyler, one of the world's most dangerous terrorists. After Tyler kidnaps a young inventor who has created a new, completely un-detectable plastic explosive, Nikita is sent to try and rescue the inventor and keep his knowledge out of Tyler's hands. When the mission is unsuccessful, Nikita is given orders to cancel the inventor, but she refuses. Operations decides that Nikita has crossed the line, and he purposely sends her on a suicide mission to destroy a terrorist hideout. Michael intervenes and gives Nikita the means to escape, but her freedom will change both of their lives forever.

With Michael's help, Nikita survived the destruction of a Freedom League hideout in the first season's final episode. Since then, she has been on the run from Section One. While working as a waitress, Nikita is captured by the Freedom League and used as bait to lure Section One into a trap. During a raid by a Section team led by Michael, Nikita saves Michael's life and they manage to escape together. Later, on an abandoned ship, Nikita and Michael share a night of passion. However, Michael's lies about Nikita's whereabouts are in danger of being exposed.

Section believes that terrorists are after the nuclear power source of a downed satellite. They later discover the terrorists are actually after it because it is a military satellite and it will give them access to the Pentagon if they are able to salvage it and crack the codes. Nikita grows closer to Jurgen and Section uses it to their advantage.

Section captures a mathematician in order to decode a code that is aiding terrorists in their attacks.

When Section discovers a wealthy terrorist plans to fund upcoming civilian attacks, Michael and Nikita pose as money launderers in order to stop him. However, his assistant, Giraldi, claims to be a Section operative who has been in the field for nine years and wants to be brought back in. When Nikita informs Operations, he tells her to ignore his request, but when Madeline finds out, she insists Nikita bring him in. Now, Nikita is caught between Madeline and Operations, and a man's life hangs in the balance.

When the founder of Section One comes back to destroy her own creation, Nikita must make a choice between the life of Michael or the existence of Section.

Nikita has a new mission, to get David Henderson Williams, Vacek's associate. She also learns more about Michael's history with Elena & Simone. Elena offers Nikita to stay with her & Michael. Nikita accepts, but she doesn't feel too cozy after her thoughts & memories get the best of her. More problems come about as Vacek misses a meeting.

Nikita continues to show evidence of the "reprogramming," including ordering the elimination of a captured Section operative and endangering the lives of children during a mission, and taking part in the beatings of a captive. Michael is determined to reverse Nikita's reprogramming, and he soon determines that the former Section operative who came up with the "reprogramming" process, Ross Gelman, may be the key. Meanwhile, Operations couldn't be more proud of the "new" Nikita, but Madeline is still worried. Eventually, Operations concludes that Michael's attempts at restoring Nikita have gone too far, and takes extreme measures.