I do not own any characters associated with the TV show Numb3rs. This story is for entertainment purposes only.

Present

Charlie and Isabel just stared at each other while everyone around them was left to wonder. Don was the only one who felt comfortable asking the obvious, "You two know each other?"

Neither of them responded for a moment, then Isabel blinked and looked over at Don. "Charlie and I worked together on a case a few years ago."

Charlie said nothing, only sat there and stared at Isabel. "I'm sorry, but would you excuse us for a moment? Charlie, can I speak to you?"

Charlie nodded and got up to leave, but still said nothing.

They left the room, walking around the corner where they would be out of ear- and eye-shot of everyone else.

Charlie opened his mouth and then closed it a couple of times as he was trying to figure out what to say. He'd nearly passed out when he looked up and saw her standing there. After all, he hadn't seen or heard from her in two and a half years.

"Charlie, I'm sorry, I realize this is a shock."

Suddenly, Charlie found his voice. "A shock? Is that what you call it? For all I knew, you were dead!" He said the last few words much louder than the first and several people began staring in their direction.

Isabel quickly looked around and pulled him into an empty conference room. "Charlie, please, we can't do this here."

He rubbed his eyes and ran his hands down his face, attempting to collect his thoughts. "Isa, I…"

"I promise; we can talk later. This is just not the place for this conversation."

"How am I supposed to go back in there and work with you right now?"

"I don't…I don't know."

"How could you…how can you be here and not have at least called me?"

"Charlie, please try to understand…"

"I've been trying to understand for the past two and a half years!"

Isabel closed her eyes and took a deep breath. "We have to go back in there and get to work, Charlie. People's lives are at stake and there are bigger things that need our attention right now."

She watched as the emotion left his face. "You're right. This is more important than you and I."

"Charlie, that's not-," but he was already out the door. "-fair."

Letting out a heavy sigh, Isabel followed him back into the other room.

Everyone turned and looked as Charlie re-entered, Isabel close behind. Don couldn't remember the last time he saw his brother with that look on his face. It was the only look that when Charlie had it, Don stayed away. He hadn't seen it in years, and if his curiosity was piqued before, it was killing him now. Who was this woman who had such a profound, albeit negative, effect on his brother?

Charlie sat back down at his computer, not saying a word. Amita tried to catch his eye with no success. He wouldn't look at anyone.

Isabel did her best to maintain her calm composure, as though her life hadn't just experienced a major upheaval. "I apologize for the interruption, Agent Eppes, you were going to go over the rest of your information with me?"

Don snuck a quick glance at Charlie, who was trying desperately to get back to work on his laptop. Don knew his brother well enough to know he wasn't getting anything done right now. He had about a hundred questions he would have liked to ask this woman, but this was not the time. They needed to get down to business.

"Yes, I'll show you what we're working on over here." Don and Isabel walked over to the far wall as he went over the maps and more of the details of the case.

Terry fidgeted in her seat. Being who and what she was, it was her job to be very in tune with those around her, and right now it was making her very uncomfortable. The tension was so thick in the room you could cut it. She'd grown rather fond of Charlie in the time they'd worked together and found she often thought of him like he was her own brother. She didn't like seeing him so upset. It had been very obvious to her the moment that the two saw each other that there was significant history between them. She was reminded of the time Kim and Don saw each other. Although she still didn't know all the details of that little piece of Don's history, she knew enough to know it had been serious. She wondered just how involved Charlie and Isabel had gotten while they worked on that case.

Lost in her thoughts, Terry jumped a little when Charlie tapped her on the shoulder. He forced a smile when she turned and looked at him, but she wasn't buying it for a second.

"Look, I left some of my papers back at school. I'm going to need them if we're going to go back over all of our work. So we're going to just work over there. I'll call Don if we come up with anything useful." He nodded toward his brother and added, "I don't want to interrupt him."

"Okay, Charlie, I'll let him know." Don was deep in conversation with Isabel and didn't seem to notice Charlie and Amita leaving.

Terry watched them walk out, knowing damn well that Charlie hadn't left anything behind at school.

When the door closed behind them, Don turned around and quickly scanned the room. "Where'd Charlie go?"

As innocently as she could, Terry replied, "He and Amita left some papers they needed at school so they're going to finish up there." She saw from the flash in Isabel's eyes that she knew it was a flimsy excuse too.

Don, however, didn't seem to care what it was. He was annoyed. "Did he say he'd be back?"

"No, he said he'd call you if they came up with anything…'useful'."

Don turned back to Isabel. "Well, until I get some updates, I guess that's as much as I can give you right now."

"That's fine, don't worry about it. If you don't mind, I'd like to take some of these case files with me to look over. I have a meeting I need to get to." She glanced at her wristwatch. "I can bring them back to you first thing tomorrow, hopefully with some ideas."

"That's fine, take what you need."

Isabel grabbed the stack of files Don had briefly run through with her. "I'll see you tomorrow then."

"Yeah, thanks."

As soon as she had walked out the door, Don and Terry exchanged meaningful looks.

"Alright, Terry, professional opinion: what the hell was that?"

"I can only speculate. I think you're going to have to go to the source if you want to know the truth."

"Yeah, that's a conversation I'm looking forward to." Don hadn't forgotten the whole incident with Charlie and Kim, and he was dreading having to pry into his brother's history. He had a few guesses at the story, based on his own experiences, but he had a hard time believing Charlie and Isabel had ever been…involved.

He sat down with Terry and David and got back to work. As important as his brother was, he couldn't afford to be distracted by him right now.

When Charlie and Amita got to her car he said quietly, "Would you mind just dropping me off at my house? I don't think I can work on this anymore today."

"Um, okay."

"Thanks." Charlie got in the passenger's seat and closed his eyes. He was thankful Amita wasn't asking any questions; though he was pretty sure she probably wanted to.

They drove in silence to his house, Charlie feeling like someone had just punched him in the stomach. He still couldn't quite believe that he'd just seen Isabel. His life had just started to get back to some semblance of normal, and there she was.

"Charlie?"

Charlie opened his eyes, realizing they were parked outside his house. He grabbed his things from the backseat and got out of the car.

"Thanks Amita, I'll see you tomorrow."

"Sure."

He started to walk up the steps to his house. "Hey, Charlie!"

He turned around to look at Amita. "Yeah?"

"Are you okay?"

"I'll be fine. Don't worry about it. See you tomorrow."

Amita eyed him suspiciously, but nodded and drove away.

Charlie walked in the door; his father was sitting in a chair reading a book.

"Hey, Charlie."

"Hey, dad."

"You're home early."

"Yeah, well, work didn't go that well today. I figured I'd come back here and sort it out."

"Oh, sorry to hear that. Is your brother coming for dinner?"

Charlie realized he'd forgotten to ask Don, but then he thought about what had just happened at the office. "Yeah, he'll be here."

Alan watched as his youngest son dragged his bag upstairs. He wondered just how bad his day had been. He hadn't seen him look that down since…well, in a long time.