Disclaimer: I don't own either Numb3rs or Stargate Atlantis.

A/N- I should have clarified myself in the first chapter. I haven't found a Numb3rs/SGA crossover on this site. There are actually two others out there that I did find, The Lost Colony by Joolz and Classified by Dira Sudis. Don is in this chappie. I figure he and Charlie go hand-in-hand. It just isn't Num3rs without both of them.

Elizabeth stared at John and Charlie each respectively. They both kept babbling on, finishing each other's sentences about how much good their new idea of tracking the Wraith would be.

"We could be saving lives!" Sheppard shouted.

"Lot and lots of lives! Think of how many people…" Charlie added.

"People that could live to old age naturally rather than becoming some mummy husk."

"Alright, I get it. But how do you plan on actually doing this?" She asked.

"We're still thinking about that. But I should come up with a plan…soon." Charlie replied.

"Still thinking about it? So over lunch you and Colonel Sheppard come up with this brilliant plan of tracking the Wraith which you are now proposing to me without any clue of how to do it."

"Sounds about right. But Charlie said it could be done so I think we should do it."

"And what exactly are the chances of us succeeding in this?"

"I can already tell you the numbers were never in our favor. But that doesn't mean we shouldn't try. It's possible with a lot of time and effort. We can do this."

"Alright. You have a go. But I want a plan on my desk ASAP."

"We can do that." Sheppard and Charlie said at the same time.

"Now, I think you two have a Wraith tracking plan to get started on and I have reports to finish before the next data exchange. I'll arrange for Rodney to give you space to work Charlie. Both of you, make this work, and we'll all be indebted for a very long time."

"We will. I can do it. Just give me time."

"He's right. There's enough brains between the two of us." Sheppard smiled waiting for a reply.

"But I suppose I have the greater percentage of brains."

"Touché my dear Charles."

"Excuse me gentlemen, but I have to get back to work."

"I think that's our cue to leave."

"I don't have hypersensitive hearing Shep." Charlie responded to the whispering voice in his ear.

"Let's go before we over stay our welcome. Nice talkin' Elizabeth."

Lt. Col. John Sheppard and Dr. Charlie Eppes walked out the door. They were excitable together. Each had played off of the other in the proposal. It was a long shot but she was going to give it a heads up. Who knew, it could work. Elizabeth took another look at the talking duo currently jogging away from her office. She shook her head.

"Why do I feel like those two plus Rodney are going to be giving me bigger headaches?"

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"So now that we are partners in crime, mind if I give you the grand tour?"

"Lead on."

"Don't mind if I do. So, what makes you qualify to come to Pegasus besides the fact that you obviously are a super geek?"

"More than you know."

"How so?"

"I have a higher overall security clearance than any of the other scientists here."

"Because of your work with the FBI?"

"No, more because of my work with the NSA and CDC."

"NSA and CDC?"

"Yes and if I told you I would have to kill you. It's all above your head anyways."

Sheppard went quiet. Still, curiosity gleamed in his eyes. He chose to place Charlie in the "my geek" file in the never-ending John Sheppard filing cabinet. Currently, that file included a meager three names: Rodney McKay, Radek Zelenka, and now Charlie Eppes. All other geeks and nerds A.K.A. scientists on Atlantis were classified as "geeks warranting protection as part of job." Kavanaugh had his own file labeled simply "other" and so help John should he ever see that whiny almost Wraith-like face again. It was going to be fun working with his new geek. Yes, Charlie belonged to him and he was going to make it clear that any military personnel borrowing said geek would return borrowed geek or else. He looked up to see his new geek frozen in place.

"Charlie? Something wrong?"

"Do we have chalkboards or at least whiteboards? I work better with them or else you'll be seeing equations all over the windows."

"I can arrange it. Anything else you need?"

"Yeah. You remind me of my brother."

"That's a good thing, right?"

"Don was my rock back home. I left to prove that I really could be independent and I know I can. It's just…"

"Go on."

"I have a tendency to get lost in the numbers."

"Everyone here, especially the scientists, have a tendency to lose themselves in their work. It's part of who we are." John spoke seriously placing a reassuring hand on Charlie's shoulder.

"That's the norm here. Atlantis is unusual. But we make it."

"P vs. NP. I get lost in it."

"Isn't that one of the Millennium problems? It's considered unsolvable. What are you getting at Charlie?"

"I can get really into my work and be so focused that I seem lost. But lost…for me anyways…is really serious."

"How serious?"

"I withdraw. I don't eat. I don't sleep. I just work on an unsolvable equation night and day. It can go on for a long time, months even. Someone…someone has to pull me out. It can take a group effort but it has to be done."

"Don't worry, I got your back. If not me, Beckett is always a willing mother hen. I'll tell him to have a haldol needle with your name on it."

Charlie smiled seeing the playful grin on Sheppard's face. Everything was going to be okay here. Yes, he was going to be okay and prove once and for all that Charlie Eppes was independent and could find work elsewhere, in a very far away elsewhere.

"Yep. You're just like Don."

"So what is you're brother Don like?"

"He's an FBI agent."

"Really?"

"He has his own team in Los Angeles. Don had me consult with him on a lot of his cases. There was this one case involving a high stakes bank robbery…"

"I'm listening."

"Anyways…"

The pair walked aimlessly through the halls. Each listening and telling stories with the other about life back home and here.

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Meanwhile in Los Angeles:

Special Agent Don Eppes stared at his computer screen. Nothing. It was yet another dead-end in his latest case. A serial killer beheading military personnel was on the loose and posting the video of the killings on different websites. So far, the FBI computer techs had come up with nothing. He could really use Charlie right now. Charlie, that was another mystery to be dealt with. He had disappeared over six weeks ago. No note, goodbye, or any clue where he was. Don was at a loss in his search for his brother. All he had turned up was that Charlie had gone gallivanting with the USAF.

"Hey. Any luck?" Don knew Megan was implying his brother more than the case. The whole team knew the case was going almost nowhere.

"No. Last tip on the case came up nothing. And Charlie, if only he knew how worried everyone is. He told no one where he was going. Dad's frantic. And you know well enough how Larry is."

"Don't worry. Things will work out."

"Thanks Megan. I just don't get how he disappeared like that. It's like he's been planning this for months. He started acting a little funny after the Kraft incident. I have this feeling that something has been off."

"Yeah. It seemed like he was trying to track Kraft and prove him absolutely wrong. Charlie was offended when we gave the endorsement. Larry said something about him continuing his search after we closed the case. Do you think he would use his clearance for something so trivial?"

"Not normally, but in that case, yeah. If he did, what did he find? So far I got nothin'. Maybe Samuel Kraft is the key. He was part of a CIA psychic program. What was it called again?"

"Star Gate. They were trying to train psychics to spy using ESP. The program was shut down. There just weren't enough results to keep paying for such a high price program. Charlie thought it was all a great hoax and a big waste of taxpayer money."

"Star Gate. I think I'll start there and see where it goes with the Air Force. He made connections somehow. I've got to find him."

"What are you going to do if you find him?"

"Beg him to come home. Tell him that people are dying. This guy is killing more and more. So far we got 12 dead and with these patterns, another tape should be showing up in five hours. Charlie can't say no and if he finds out what Dad has been doing, he'll come home. I just gotta find him Megan. He needs to know that we all miss him."

"Just don't get over you're head, Don. I know you and your father and brother. It must run in the Eppes' blood 'cause you seem to attract trouble. Be careful."

"I will. Don't worry."

She hoped so, 'cause Alan Eppes would crumple if he lost both sons. It was bad enough not knowing where Charlie was. Whether he realized or not, everyone considered him a part of the team. The time Charlie spent here almost made him a bona fide agent. This was beyond her but she, David, Colby, and the rest of the team were going to make sure Don didn't get too obsessed in this. If Charlie got lost in numbers, his brother got lost in serial killers and family matters, not a good mix.

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Back in Atlantis

"This, is your new workspace. Your own private lab and per the delightful Colonel Sheppard's forcible request, you now have over half of the chalkboards, whiteboards, chalk, board erasers, and dry erase markers. I hope it's enough."

"For now. Thank you Rodney. This will do well. I have more space than my garage."

"Eh, what else am I going to do for the only other intelligent person in the city?"

The room was huge. He had a feeling that McKay had picked it out knowing that the project meant being bogged down quite a bit and therefore the need to move around was absolute. One corner revealed a cot with pillows and blankets already laid out. There were laptops situated on a nearby counter not far from the bed. Charlie was even lucky enough to have a balcony connected to the lab. Were they trying to promote complete focus on his work? He wouldn't complain though. For Charlie, the set up of the room gave the best possible lighting and a good view of the city out of the windows. It was the ultimate mathematician playground. Thinking twice, it felt more like going on his first roller coaster ride knowing how everything worked and yet the adrenaline feeling was beyond conventional equations.

"Here, we tend to live in our work. Don't be shocked at all when you find yourself sleeping in that cot or when Carson or one of his minions comes bearing a tray of food because they know you will refuse going to the mess hall short of a military escort. That by the way is rather annoying to us, and to the Marines. Anything else you can think of?"

"No. It's all perfect. I could hole up here for a very long time. Don't worry though, I still have to go offworld and change clothes so I'll get out sometimes."

"Good. We wouldn't want the powers that be on you anymore than they are on me."

Charlie laughed. He felt good. This was a dream come true for him. He had the ultimate math project to work on. The good thing was that once the algorithms and equations were finished it would only be a matter of simple adjustment and the same principles could be used on Earth to track criminals or suspected terrorists. Only one last thing was left on his mind, how were Don and his Dad? Charlie knew Don would be looking for him and he wouldn't put it past his brother to find him here. Don had that kind of determination. He just wouldn't think about his brother, rather he would work on bringing down the Wraith with a new weapon of prediction, numbers.

"I think this is worth it. But I have to agree on the powers that be in the forms of Beckett, Weir, and Sheppard. I really would hate to be you."

"We have some intelligence coming in from the alpha site for you. It's just a little something to get started off of. I assume you already have variables planned out in that math tinkering mind of yours."

"Yes. I have over 1,000 different variables planned. It never hurts for accuracy. The more I have the better I can pinpoint and predict the Wraith's actions. We need probability in our favor without having to worry about the classic Monty Hall problem."

"1,000 plus variables. I'm just glad it's you working on this little project and not me. I wouldn't have time with everything else I have going on. Sheppard wanted me to tell you that he has you on with us tomorrow going offworld. The briefing is at 0800, be there, on time. Let's just say it's not a good idea to be late."

"On time, right. I'll see you then. I'd really like to get started on this."

"Until then. Oh, and uh don't let any nincompoop know where this area is. I have my own secret lab a little ways away. It's nice to have your own space and no one else needs to know."

"Sure thing boss."

"See you later chum."

Charlie waved goodbye and tackled the whiteboard in front of him with equations bounding from his mind. He had a lot of work to do. The clock was ticking.