A/N – This chapter starts during Day Three, and involves a slightly revised version of the day's events. This is a oneshot story and doesn't affect any other fanfiction of mine.

1.31am, CTU Los Angeles

Chloe O'Brien had never experienced such a day, and as far as she could tell, this day was far from over. She had only worked at CTU Los Angeles for a short time, but had hoped that she wouldn't have to face such a major threat so soon – the events of a few years before had been repeated to her by numerous CTU agents and employees, even though she had never asked any of them to do so. Sighing quietly as she walked briskly down a dark corridor towards Tech One, eager to stop the worm that Nina Myers had planted in their system and also eager not to let someone else beat her at anything even remotely connected to computers, she didn't notice that someone was following close behind, until that person knocked against an exposed pipe as they tried to keep quiet. Stopping for a moment, and turning around slightly, Chloe narrowed her eyes and examined the shadows.

"Is there anyone there? I don't have time to be playing games, whoever you are!," Chloe snapped, before turning around and continuing her hasty walk towards her destination, and she had almost turned the corner into the well-lit area around Tech One, when a hammer was brought down hard onto the back of her head, sending her crashing to the ground. The attacker and would be murderer of Chloe O'Brien then dragged her body into a deep alcove, took a deep breath and smashed the hammer down as hard as they could into her head once more. Listening out for any breathing – or anyone likely to discover the grisly scene – the attacker left the alcove quickly, disposing of the hammer into the air vents. As her blood pooled around her body, Chloe's eyes stared at nothing.

In Tech One, Adam Kaufmann was distracted from his own work of trying to defeat the worm, looking over at the door and waiting for Chloe to walk through it. Although he found her to be a pain in the ass as well as a rather anti-social person, he respected her work and talent with computers immensely, and he was concerned that if Chloe wasn't in the room soon, the worm would complete it's purpose, leaving hundreds of undercover CTU agents at risk. Cursing under his breath, he grabbed the phone and dialed Tony's extension.

"Tony, where's Chloe? We're losing time!," Adam spoke as soon as Tony replied, his voice loud and stressed, his eyes fixed on the door.

"She's not there yet? She left the bullpen ten minutes ago, she should be there now. You've checked that she's not in any other room, right?," Tony replied, his own eyes panning across the large, busy bullpen. Noticing a guard with a shocked look on his face, he asked Adam to hang on, curious as to what the guard wanted. Walking up close to Tony, the guard seemed eager not to broadcast his news.

"Director Almeida, can you come with me, please?," The guard spoke with a Seattle accent, and nervously ran his fingers through the mousy brown hair that framed his thin face.

Sat at his desk, Alex Myers watched the guard and Tony leave the bullpen, and he took a deep breath. The worm was minutes away from succeeding, and Nina was minutes away from either being freed back in Mexico, or brought back to CTU and a high risk of being killed. He gazed at the blank screen of his computer, and tried to think of what his options were. If Nina were to be let loose in Mexico, it was a certainty that Jack would go after her almost immediately after the threat was over. If she was brought back to CTU, then anything might happen. He looked over at Kim and wondered what was going through her mind. Jack had been able to get her a job at CTU to keep her safe, and only months after starting she was doing well in the midst of a crisis that involved the killer of her mother.

Tony's hand was placed over his mouth, his eyes wide and full of the same shock that he had seen in the guard's eyes back in the bullpen. He was looking down at the corpse of Chloe O'Brien, and for a fleeting moment he forgot about the virus, about Nina, about the worm. Removing his hand from his face and bending down, he gently closed Chloe's eyes.

"We'll find out who did this, Chloe. I promise you," he whispered.

1.45am, Jack and Nina's plane, above Southern California

"What?," Jack rasped into the phone as Tony informed him of Chloe's death. Unable to believe it, he sank into a seat close to Nina, who was watching with some curiosity. She had heard Jack speak only one word during the conversation, and she could only guess as to what the call was about, and as Jack hung up, he stared at the opposite wall of the plane, and Nina debated with herself whether to ask about it or not. It didn't matter anyway, as Jack noticed her gazing at him.

"If you don't stop that worm right now, Nina, I swear I will kill you right here, no matter what," Jack whispered, staring straight at her as he spoke. She frowned, before turning away and looking at the laptop. Seconds later, she turned back to face Jack, who looked ready to jump out of his seat and beat her to death.

"What was the call about, Jack?," Nina asked, and realised that it was a mistake as Jack did indeed leap up out of his seat, before grabbing hold of her neck.

"Someone inside CTU murdered Chloe O'Brien, a good agent as well as a good friend of mine. Now, you wouldn't know anything about that, would you Nina?," Jack spoke with his face close to hers and his hand tight around her neck, his voice low and threatening. The look on her face convinced him that she didn't, but he still held on to her.

"Jack, whoever did it wasn't doing it for me, I promise! Look, we can still both get what we want out of this," Nina spoke, her voice affected by his hand crushing her throat.

"Nina, right now I need you to stop that worm, and then maybe we'll see about what you want out of this!," he spoke, before a bleeping sound from the laptop caught his attention. Letting go of her neck, he left her to recover as he turned around and saw the message on the screen. Yelling in anger, he smashed the laptop off of the makeshift table, sending it crashing to the floor. Turning around, his eyes wildly staring at Nina.

"Do you realise...do you REALISE what you've done, Nina?," Jack snarled, and Nina decided that she needed to calm him down. She noticed Chase Edmunds walk up to Jack, but even he seemed fearful of Jack. As Jack sat down next to chase, he was amused by the look on Chase's face and smirked. Turning around, he saw Nina holding the laptop and typing away quickly, hoping that she had been scared enough to stop her worm.

1.55am, CTU Los Angeles

Tony had just gathered the agents and staff together in the bullpen to inform them of Chloe's death, and as he gave them the news, he looked around the crowd, at each of the faces. If he could just spot a flicker of guilt, or a look of shame on one of the people he was stood in front of, he would at least be able to consider that person a suspect, but he noticed nothing. He had no reason to suspect anyone, as well as having no idea if the killer was even still in the building. As the crowd dispersed and people went back to their stations, all Tony could do was await any news from Forensics, who were busy scouring the crime scene.

Alex looked at Tony over his computer monitor, and was wondering whether there would be any evidence found of the killer, before noticing his screen flicking back on. It looked, as far as he could tell, that the worm had been shut down. He had no idea if Nina was either on her way back to Mexico, or back to CTU.

2.00am, Jack and Nina's plane

Nina sighed quietly as Jack and Chase conversed quietly elsewhere in the plane. She had to stop her worm seconds before it could have done the damage she really wanted it to do, and worst of all, it appeared as if she was on her way back to CTU. She couldn't help but wonder who had killed that O'Brien woman, and if it had anything to do with her and her worm. Seeing Jack walk up to her, she wanted to roll her eyes but decided against it. Handing Jack the laptop, she looked up at him with a look of anger and hatred that she knew he would never have dreamt of seeing just a few years before. Back then they had been the best of friends, but now they had travelled straight to the extreme opposite, and were now deep enemies

"We're taking you back to CTU, Nina. If you tell us where Alvers and Amador are, I'll consider getting you some sort of deal. Is that understood?," Jack spoke, his voice calm. She looked up and nodded, knowing that she had to wait for the next opportunity, something that she wasn't going to find stuck on a plane high in the sky. As Jack turned around and left her alone once more, she juggled the information she had received about CTU since the surprise and mutually unwanted reunion with Jack at the auction. She knew that they would want to interrogate her – and probably torture her as well – and considered what sort of deal she would get from Jack. Nina, not being foolish, knew that any deal from Jack would involve a lengthy stay in jail anyway, leaving her a sitting duck for anyone coming after her to make sure that she couldn't give up too much of her intel. It would be better, she reasoned, to be free and at least be able to move around and avoid any would-be attackers.

As Jack sat down, he examined the laptop and allowed himself a small smile as he saw that Nina had indeed stopped the worm. He had taken a risk by leaving her alone with the laptop and no instruction to stop her worm, but he knew Nina enough to know that she would do what was in her best interests, and Jack had made sure that at that moment in time, turning off her worm was certainly in her best interests, and more importantly for Jack, the interests of CTU and their small army of undercover agents.

2.05am, CTU Los Angeles

Tony had confirmed that Jack and Nina's plane was coming to Los Angeles, and that Nina would be interrogated at CTU, and Alex realised that Nina was running out of time. He felt helpless and had no idea what he could do to prevent Jack from killing his sister, and he certainly had no way of stopping that plane from landing or Jack from bringing Nina in. Taking a quick glance over at Kim, he considered the possibility of Kim coming face to face with her mother's killer for the first time in over four years.

Kim herself was nervously waiting for her father to return to CTU. It was bad enough that he was out in the field risking his life without the fact that he and her boyfriend were in the same plane as Nina Myers. It had been a terrible night, made even worse by Chloe's shocking murder, and she wondered if the murderer was amongst the numerous people working around her, as well as why had they killed Chloe. Certain that it was because of the worm, Kim considered the possibility of there being a mole inside CTU working for Nina, something she dreaded.

Morris O'Brien, Chloe's ex-husband, was with her body in the morgue, a silent tear running down his cheek as he held his former wife's cold hand in his own. His brown eyes were filled with tears, but he was trying hard not to lose it. Although a guard had offered to stay inside the morgue to protect Morris from the murderer, he had politely refused, and the guard was stood outside the morgue.

"God, Chloe, I didn't think you would die before me, sweetheart. I thought the drink would kill me long before, but now I wish I never touched a single drop. I lose you, Chloe, and now I will never find you again, and I don't know what to do, Chloe. I can't do anything to bring you back, I can't do anything to go back in time and stop myself from becoming some pathetic drunk," Morris whispered, before sighing. He closed his eyes for a second, before turning around.

"Goodbye, Chloe. I promise to never go back to the way I was," he spoke, before walking slowly towards the door of the morgue.

Back in the bullpen, all of the attention was on Jack and Nina as they walked through the building towards the holding rooms. Nina stared at Kim as she passed by Jack's daughter, before noticing her brother. Alex was looking at her, and he wondered if Nina could tell something from his face that noone else could, and he hoped that if she did, that she kept quiet.

2.30am, Holding Room 1

The interrogation had been going for some time, and Alex had joined Michelle in the surveillance room. He watched as Tony questioned Nina, and he looked directly at Nina's face. She seemed so confident, so defiant and Alex knew that Tony would probably soon be resorting to torture to get the needed information.

"Do you think she knows anything useful?," Michelle asked Alex, her own gaze directed at Tony, who looked stressed, angry and quite probably troubled by thoughts of the day Nina's treachery had been uncovered.

"I don't know," Alex replied, before noticing someone walk in with a silver briefcase, and he knew then that torture was about to be used on Nina. Whether it would be effective was unknown – after her imprisonment, Nina had been tortured numerous times in CTU's attempts to get information from her, but she had given them little by the time of her pardon.

"What sort of deal can we offer her? I can only see us giving her life without parole instead of the death penalty," Michelle spoke. She had seen Jack's face as he told her of Nina's pardon all those years ago, and she knew for a fact that any deal this time would certainly not be anywhere near as generous and, if she was being honest with herself, she thought that Nina would be lucky to get anything other than a short sentence before being executed at the first possible date.

In the bullpen, Kim was watching Nina's interrogation via video link on her computer. It wasn't that she particularly wanted to watch what was going on, and she certainly wasn't enjoying it, but she felt the need to witness it, to hear for herself what Nina said or didn't say. She tried not to look for too long at Nina, but felt herself pulled towards Nina's face, a compulsion to do so overriding her hatred of the woman.

As the needle was pulled slowly out of Nina's neck, she winced quietly and braced herself for the next painful stab. She heard Tony ask her if enough was enough, and she decided that she had to do something quick, something drastic that would disturb them enough to somehow open up a window of opportunity for her to get out of CTU.

"This should be enough," she stated flatly, and forced her head back violently onto the needle, slashing her carotid and causing her to spasm uncontrollably. Horrified, Tony had not expected that. With her blood splattered all over him, he tried to hold her steady, hoping that Nina could be taken to Medical in time. Alex, who was watching the scene with horror behind the mirror, felt helpless as he saw his sister's life beginning to slip away.

Nina was trying desperately to retain conciousness as she listened to the panic around her. She could hear Tony's voice, the noise of quick footsteps as people rushed around her. She could feel the warm hands of some woman holding her, and Nina wondered if the woman knew what she had done, or even who she was. As she was placed onto a stretcher, she looked up at the ceiling with her eyes partially closed. The lights merged together in one fluorescent line as she was briskly moved towards Medical. It was only a short journey, and she was soon inside Medical and soon transferred from the stretcher to a operating table. The noise around her changed from frantic agents to medical talk, and she knew that the agents had all left her. Squeezing the tube that was meant to feed the anaesthetic to her veins, she closed her eyes and waited for them to at least get the bleeding under control. Seconds later, she opened her eyes wide, grabbed at a scalpel and leapt from the table, slashing at every other person in the room. Leaving just one alive, she made her way out of Medical and down a dark corridor.

Alex was now stood close to where Jack was being interviewed, watching the events as he tried to work out what was being said. Suddenly, an alarm began to blare throughout the building, and he knew for sure that Nina had begun her escape attempt. Quickly making his way towards Medical, he could only hope that if she was to caught, that Jack would not get a chance to even lay a finger on her.

"Nina?," Alex called out as he entered Medical slowly, only to find a bloodbath and the bodies of almost all of the medical staff. Soon joined by Tony and Jack, he saw a nurse cowering in the corner of the room. She pointed towards a corridor, and the three headed off after Nina.

Kim looked around as the chaos grew inside CTU, and she realised that her father had gone after Nina. Deciding that she had to do something, she ran into a corridor and began searching for Nina, her CTU issued gun at the ready.

Nina herself was in a room which she knew all too well – it was the room where she had killed Teri Bauer, and now she was pulling away at wires in an attempt to turn off the alarm.

"Nina," Kim spoke quietly but firmly, her gun pointed straight at the older woman, who turned slowly to face her. Smirking, Nina contemplated whether or not to shoot Kim, although she wondered if she could really be that cruel to Jack.

"You won't shoot me, Kim," Nina spoke, almost demanding that Kim put down her gun and walk away, a threat to Kim making clear that she was prepared to shoot her.

"Dammit, Nina!," Kim spoke, her voice louder and more nervous this time. Nina smiled, and slowly began to raise her gun. Kim, trying to remain calm, was trying to build up the courage to shoot, when a shot came out of nowhere and hit Nina's right shoulder, sending her to the floor. Shocked, Kim looked at where the shot came from, and noticed her father.

A few hundred metres away, Alex heard the shot and froze. He wondered, hoped, that it didn't signal the end of his sister's life, and tried to find where the shot came from. Running down the corridor, he could hear Jack, and as he turned into the room where Jack and Nina were, he saw Jack fire three bullets into his sister. A few moments of silence occurred, before Alex walked into the room.

"Jack?," Alex spoke, catching Jack's attention. Looking at the younger agent sadly, Jack stood up and walked towards Alex.

"I'm sorry, Alex, but I had to do it," Jack replied, and Alex could feel the anger rising in him. The shot he fired into Jack's body was quick and sudden, and as Jack lay on the ground, stunned and defenceless, Alex looked down at him with a look of pure fury.

"Dammit, Jack! You just had to have your petty revenge, didn't you?," Alex yelled at him, his gun pointed at Jack's chest and ready to end his life. Jack looked up at him with shock.

"Alex, please calm down! This doesn't have to get any worse, OK? Please don't do this," Jack pleaded with Alex, who suddenly did look calmer, much to Jack's relief.

"Jack, I'm afraid I'm doing this whether you like it or not. It doesn't matter anyway, I've already done this once before tonight," Alex spoke, and Jack didn't know what he was referring to at first.

"You son of a bitch! You killed Chloe!," Jack spoke, shocked and angry. Alex, who knew that he had to kill Jack quickly, simply smirked.

"Yes, Jack, and she died unnecessarily, because of you," Alex spoke, and he was about to finish off Jack before he heard guns click behind him. Freezing, he didn't dare move until he could be sure no one was behind him.

"Drop the gun, Alex!," Tony demanded, and Alex complied, looking at Jack hatefully as Tony moved up to Alex and handcuffed his hands behind him, and as Alex was led away from the scene, Chase knelt down next to Jack.

"You OK?," he asked, concerned about the gunshot wound in Jack's shoulder.

"I will be," Jack whispered.