Jack and Chase roam the woods, searching for Nina. Chase radios Jack when he sees a light. He goes to check it out and finds a dead delta team member. Nina comes upon Chase and takes his weapon. She orders Chase to radio Jack a code six, and he obliges. Suddenly, Nina is cold cocked by Jack. He makes Chase go to the airfield so that he can "interrogate" her. Nina claims that she can help him find Amador in Los Angeles.
Although Jack looks like he is about to kill Nina, he instead calls CTU to tell Tony that he has captured her alive. Jack thinks she must know something.
Tony tells Chloe that Chappelle wants to see her. He then phones Kim to let her know that her father and Chase are returning to Los Angeles with Nina.
Chloe comes into Chappelle's office, refusing to speak about the baby. He accuses her of violating agency rules, and he threatens to perform a blood test to find out who the baby really is. Chloe still won't reveal what is going on, so Chappelle places her under guard while they run tests on the child.
Wayne lets Palmer know that Amador escaped in Mexico with the virus. He is a known arms dealer, so it is unclear what his motivation is for bringing it back to Los Angeles. Palmer is interrupted with a call from Sherry. She says that Kelly, the man willing to go public about Milliken's past, has disappeared. She believes Milliken's people got to him. Sherry is on her way to see Milliken's wife, Julia. Palmer is adamant that she not go there, but Sherry promises to stay away from Milliken and only talk to Julia.
Jack arrives at the Las Nieves airfield with Nina. Chase is a bit surprised to see Nina still alive. Jack knows that Amador is already out of Mexico, so they board a Navy plane headed for Los Angeles.
Aboard his own private jet, Amador phones a man named Marcus Alvers. He tells Alvers to be ready because he has the virus.
Sherry calls Julia Milliken, who gives her the gate security code to enter the property. Sherry orders her to disable the security cameras.
Julia goes into her husband's bedroom to find him watching the news. She tucks him in and kisses him goodnight.
Jack asks the restrained Nina what she knows. She says that Amador always deals with a man named Alvers when it involves business on the west coast. However, she has no idea who he is or how Amador contacts him. Jack asks Tony to run a check on the name.
Chase is cold towards Jack, and he accuses him of not trusting him with the secret Hector deal. Jack explains that when he pulled the trigger on Chase, he was taking a chance that Salazar would not give him a loaded gun. Thankfully, that proved true. Those kinds of choices are always a factor in the field. Now they must keep their focus on stopping the virus. Chase backs down, and wonders whether Nina really does knows more. Jack wants to wait to see if Alvers is a real lead.
CTU techie Dalton Furelle finds a connection between Amador and a man named Marcus Alvers. These two men were once suspected of manufacturing weapons-grade Anthrax but were not convicted. They have also been seen together numerous times over the last few years. Tony assigns Michelle to hook Dalton up with manpower from Division to trace Alvers.
Tony calls Jack with news on Alvers. Now they have to find him. Nina decides to admit to Jack that she knows more, and that she can help him find Alvers before he meets with Amador. She wants Jack's word that he will help her case with the Department of Justice. He agrees. Nina gives up a Felco prefix number that, when dialed, gives an internet socket where Alvers can be reached. After Jack follows her direction, nothing happens. With a slight smile, Nina tells Jack to wait.
At CTU, everyone's system locks up. All the computers go down. Tony warns the group that there is a self-propagating code leaking into their database. Back on the plane, Nina informs Jack that his dialing actually triggered a worm that will bring down agency connectivity. "Until I say otherwise, your entire anti-terrorist computer network is jammed," Nina says calmly.
Jack gives Tony the heads-up that Nina embedded a worm into CTU's system when she worked there. They don't know what Nina wants in return to stop it. Jack suggests they assign Chloe to the task of saving the network, but Tony explains that Chloe has been asked to step aside.
Nina tells Jack that she wants the plane to return to Mexico. Once it turns around, she'll slow down the spread of the worm. When she's safe in Mexico, she will give him the final kill code to end it. Jack knows that if the CTU computers go down, undercover agents around the world will be exposed. Nina warns him that they can't solve the worm internally.
Tony appeals to Chappelle for allowing Chloe to work on the worm. Chappelle begrudgingly agrees, and lets her go from custody. With Adam and Dalton's help, Chloe gets to work on the system.
Sherry arrives at the Milliken estate and lets herself in through the gate with the access code.
Sherry sneaks into the service porch and lightly taps on the door. Julia opens it. Sherry proposes that Julia help her prove that Milliken was involved with Kelly's disappearance and, possibly, his murder. If Milliken goes to prison, then Julia will get everything. Sherry needs Milliken's cell phone to see who he has called in the last few hours, but Julia is afraid to go into his bedroom. Sherry takes charge and does it herself.
Sherry tiptoes into Milliken's bedroom and goes to the nightstand next to where he is sleeping. She grabs the phone and rushes out.
Chloe hurriedly leads the group in de-worming the system. She is upset, however, that Adam and Kim stabbed her in the back by going to their bosses. Chloe says she went out on a limb in order to protect her friend's baby. "What friend?" Adam asks. Before Chloe can answer, her monitor beeps, signaling that the worm is now speeding up. Chloe tries another tactic.
Sherry reads off Milliken's last dialed calls to someone over the phone so that they can be tracked. She tells Julia that they are now done. If any of those calls can be traced to Kelly, then they will have something on Milliken. Suddenly, Milliken enters the room and sees Sherry with his wife. Sherry pointedly asks him about paying off Kelly to keep quiet about his daughter's death. "We can end it now, and you can back off David," she threatens.
With Jack out of earshot, Chase tells Nina that Jack will kill her if she tries to play him. Jack brings over a laptop and shows Nina that the worm is now spreading faster. It will bring down the whole CTU network in a few minutes. If she wants any leverage, she will have to stop it. Over Jack's phone, Nina gives Chloe instructions. This slows the worm down for another 20 minutes, but does not stop it completely. Nina warns Jack to turn the plane around or the worm will finish its task. Jack insists that they are going to land in Los Angeles and that she will help him find Amador.
Milliken and Sherry fight, and he starts to cough. When he loses his breath, Julia runs to get his pills. Sherry stops her. Milliken stumbles out of his wheelchair and gasps for air as he reaches for the bottle. Sherry and Julia watch him die on the ground.
Julia is horrified, but Sherry convinces her to say that she was in her bedroom when Milliken died. This was an accident. "You're free of him," she says. Although Julia is unsure about lying, Sherry says she has no other choice if she doesn't want to spend her life in prison. Sherry instructs Julia to call 911 after an hour and pretend like she just found her husband's body. Julia can never reveal that Sherry was there.
Chloe works frantically to stop the worm, but it is unsuccessful. Tony calls Jack to tell him that they will need to go back to Mexico to get Nina's assistance in preventing this worm from bringing down the CTU system. Jack turns to Nina for more help, but she remains silent. Chase wonders if they should just give in to her demands. The plane begins to rise, and the pilot lets Jack know that he got orders from Tony to return to Mexico.
Jack points his gun at the pilot to make him land the plane in L.A. Tony sees the plane's descent and radios the cockpit. He tells Jack that he is ordering the plane to turn around so that they can get the kill code. As Tony and Jack argue, Chloe makes some headway into defeating the worm. She succeeds, and Tony lets Jack know that they are back to being fully functional.
Jack goes to Nina smiling. She doesn't believe him when he says that the CTU system is working. But as the plane lands, Nina sees from Jack's relieved expression that this is true.
Chappelle commends Chloe on her work. Yet he says that she is still going to be handed over to the police. Chloe is alarmed when she sees the baby being taken by Child Protective Services. She agrees to tell Chappelle who the father of the baby is.
Chappelle releases Chloe after he gets his information. Kim comes up to her and asks what happened. Chloe says that since she told Chappelle the truth, there won't be any charges pressed. Kim asks who the father is. Chloe answers that it is Chase.