Author's note: You know that timeless admonition to write what you know? Well, we're coming up against a small problem here; what I know about math would probably embarrass the average fifth-grader. Any of you to whom math is not a four-letter word want to beta some upcoming math-related bits for me? Otherwise I'll just make this considerably lighter on math than the average episode, my plot will work either way.

Also, this fic was started before the airing of "Ultimatum." Considering some plot similarities, I'm going to officially set this story before "Ultimatum," otherwise the characters in this fic would have to spend a lot more time referring to the events in that episode.

EPPES RESIDENCE

Alan's eyes tracked his younger son as he walked in with his head averted from the living room, set down his messenger bag, and headed out to the garage. Without much delay, Alan removed two iced coffee drinks from the refrigerator and followed.

"How'd it go at the detention center?"

Charlie didn't answer, instead choosing to write on the chalkboard at a furious pace.

"Charlie?"

"Not now, dad."

"Yes, now. He's not just your brother, he's my son, and I want to hear how it went."

Charlie spun around in what a less familiar person might have read as anger, and Alan handed him one of the glasses, taking the opportunity to briefly squeeze his younger son's hand in a mix of comfort and appeal.

Charlie's voice was hard and high-pitched. "It went great. I broke down in front of all the guards, got Don hurt, went into crazy math obsession mode, and managed to somehow pass out on the floor to make things even more humiliating. I'll be lucky if they ever let me set foot in the place again."

Alan nodded, setting aside Charlie's disturbing outburst for the moment. "And Don? How is he coping with all this?"

Charlie took a deep breath and swallowed several mouthfuls of the coffee. "He's being – Don."

"So he's okay, then. He's hanging in there?"

Charlie nodded. "He – asked me to give Robin a hug for him."

Seeing the brokenhearted look that accompanied Charlie's last words, Alan put a soft hand on the side of his son's arm. "I don't know how I wound up with two such stubborn, soft-hearted sons. But I do know you've both gotten through everything life has thrown at you, and Don is going to make it through this."

"I hate this, you know. I just hate it. It never goes away – I – I've gotten so I can be at crime scenes without wanting to throw up or pass out, I've even gotten better at being shot at-"

"Music to any father's ears," commented Alan.

"-but I can't shake this incapacitating mental - I don't even know what - when the people I love the most need me to be – to be my best."

Alan sighed. "You know, I raised two wonderful, beautifully compassionate sons, a fact of which I couldn't be more proud. I don't think I've met a wrong in this world you two boys didn't want try and right. But there is another trait you and your brother share, both in your own unique ways, and that's your nearly debilitating tendency to make it all about yourselves when the – ah – coprolite hits the fan."

Charlie looked back at him, wounded. "About me? Dad – the reason I can't cope is because every thought I have is about Don, and what he's thinking, and what he's going through, and what if I can't clear him and he –"

Alan stopped him by grabbing one of his waving hands and holding it still. "My point is, it's Donny's future at stake here, not yours. It does appear that the application of your skills is the best chance he has, so what matters is using that gift to bring him home. It doesn't matter how upset you are, or how humiliating it is, or how you cope."

Charlie blinked, a very confused, curly-haired deer in the headlights. "And – when I can't? I – I think I passed out in there. I was having these flashbacks, and-"

Alan led Charlie over to a chair and sat down opposite him, carefully suppressing any expression of the worry it caused him to feel Charlie's hands shaking, or to hear his comment about getting Don hurt. "Then you sit there and go through whatever it is you have to go through. People understand more than you think, Charlie. To be honest, it's probably a relief to people that there are some things you aren't good at. It makes them like you, not look down on you."

"I try so hard not to embody the stereotypes. Crazy mathematician. Academic with poor social skills. Arrogant genius. Helpless little brother. I – turned into most of those today, and –" he threw up his hands. "There I go – making it about me again."

"You know another wonderful thing about you and Donny? You both listen, and you learn from your mistakes." The elder Eppes sipped at his coffee. "I would appreciate it though, if you'd spend as little time as possible heartsick, and as much as you can getting my son out of jail. I need him to help me transplant those hedges."

BULL PEN, FBI OFFICE, TWO DAYS AFTER DON'S ARREST

David looked up with a weary smile of greeting when Charlie half walked, half stumbled up to his desk. The young professor was unshaven and had exhaustion written all over him, but his gaze was clear and intense. "Any progress?" David asked.

"Yes – and no," said Charlie. "This recording – I'm ninety percent sure they took recordings of Don saying those lines, probably on his cell phone, at different times and in completely different contexts, and spliced them together with recordings of our setup guy."

"Can you prove that in court?" asked Colby.

Charlie rubbed his forehead. "No," he admitted. "Not mathematically, and not in court. This is more of an informed hunch. The thing is - I need permission to send it outside the FBI."

"Where to?" asked David.

Charlie shifted uncomfortably. "To Fort Mead. This composite – it's very, very good, and I think I need their help. They have far more supercomputing power than Cal Sci, and one of their guys specializes in this sort of thing."

"No offense Charlie, but why is the NSA going to be interested in this case? It's way off their radar," said Colby.

Charlie gave him a slightly embarrassed look. "I – ah – I'm one of their more valuable consultants." He glanced away, as was his tendency when trying not to sound arrogant about his status. "I've got friends there, and they owe me some favors."

"Okay," accepted David with a small grin. Sometimes it was easy to forget that Charlie was one of the top minds in the world; a person just wasn't accustomed to someone of Charlie's stature hanging around an FBI office solving murder cases.

"Wait – I thought the best geeks were all working outside the Triple Fence these days," said Colby.

Charlie's half-smile contained a gleam of mischief. "Supposedly."

"Jesus Christ, is there any agency you don't work for?" asked Colby.

"Well – ah – the CIA and I had a falling out a while back," said Charlie, wincing. "I might have used language that Alan wouldn't be proud of – let's just say if a few individuals in that agency were to vanish, I wouldn't have too much of a problem with it."

David and Colby exchanged glances, and David stood. "I'll go talk to Victor Nychev about the recording."

CAL SCI, CHARLIE'S OFFICE, THREE DAYS AFTER DON'S ARREST

Amita massaged Charlie's shoulders, bending over to kiss him on the cheek. "You look exhausted. Have you even slept since Don was arrested?"

Charlie turned his head and kissed her back. "Not officially. It's going to take so long to enter all this data as the FBI gives it to me, I want to make sure all the TAs are up to speed on what to enter, and I'm still debugging this program –"

"I can help you with the debugging," said Amita. "Why don't you take a nap, and let me finish it."

Charlie closed his eyes, his head drooping. "Okay. I just – I'm finding it hard to work here. I feel like I should be at the FBI, but I don't want to get in the way of their regular cases."

"Speaking of," said Amita, raising her head. "Hi there."

"Hi, Amita," said Liz, walking up to the desk. "Wow, Charlie – you look awful. Listen – I just came by because we identified a suspect, and Vic Nychev agreed to interview him. If you want in, I can drive you to the office."

WAR ROOM, FBI OFFICE

David pointed to the main screen. "See this guy? That's Cliff Howard, the dude Don sent away for murder a number of years back. Served over a year in prison before a second murder with the same MO cropped up, and Don happened to catch the case. Exonerates the guy, but not before he spends an awful lot of time thinking he's not gonna be with his family again until after his kid graduates high school."

He flashed another photo up on the screen. "This is Dave Gonzalez, he did time with our guy. They were friends, and it turns out he's got big money connections. Gang stuff, mob tie-ins – if he wanted to help a buddy by setting up Don, he could pull the strings."

OBSERVATION BOOTH, FBI INTERVIEW ROOM

Charlie felt himself tense when Nychev walked into the room, even though this time it wasn't Don sitting at the table. "What am I accused of this time?" asked Cliff Howard.

"Nothing, yet," said Nychev, sitting down across from him. "I just want to ask you a few questions about a case we're working. You remember Special Agent Don Eppes?"

Howard gave him an incredulous glare. "You don't forget the guy who sends you away for murder."

Nychev nodded. "No, I don't imagine one does. In fact, I imagine you'd think about it a lot." Howard was silent. "Maybe you'd think maybe it was time for Agent Eppes to know what it was like to go down for something you didn't do?"

"What?" asked Howard, looking genuinely confused.

"Agent Eppes has been arrested for fraud, and we're looking at evidence that someone set him up. Framed him. Now what sort of guy might be interested in doing a thing like that?"

Howard sighed, staring almost blankly at the table for a minute, considering his reply. When it came, his voice was thick with anger and regret. "Look – I know I got a record, and in cop world that means I'm automatically guilty of whatever you think I did. But I'm not some pissed-off sadist out for revenge. I don't think anybody should have to go through what I did, and if I was gonna have it out for anybody it'd be the dumb-ass lawyer that pled me guilty without looking closer at the case."

"I find that pretty hard to believe," said Nychev.

"Hey, all I wanted out of Eppes was for him to look me in the eye and tell me he was wrong and he was sorry. He did that, an' he listened to what I had to say to him. That's a hard thing for a cop to do. Yeah, I was pretty pissed when it went down, but Eppes did right by me in the end."

Nychev stood and extended his hand. "Well, I think we're done here then. Thanks for coming in, I appreciate that it was stressful given the history." After a moment's hesitation, Howard accepted the handshake.

FBI WAR ROOM

"I'm sorry, guys," said Nychev. "But we're looking at a genuine dead end here. The connection between him and Gonzalez is a bit weak, and I believe the guy. I think he's just grateful to have gotten a second chance at life with his family, I don't see him screwing that up with some revenge plot."

David reached for the remote and turned the screen with Howard's face on it off. "I'm afraid I have to agree."

All hands looked to Charlie, and after a moment he threw up his hands. "I agree. I'm not the interrogator or the criminal behavior expert, but – he seemed innocent. And I don't want to make assumptions about criminal social networks without the data to back them up, but the sophistication of this doesn't seem to match up with lower level criminals like him and his friend from prison."

Colby strangled a half-laugh, and David looked at him. "Sorry – I just had a mental image of Charlie here conducting an interrogation."

"Hey!" protested Charlie. "I've helped with interrogations before, I've been quite helpful."

Colby grinned. "Yeah. Helped being the operative word. Tell you what, we'll put you in the box with the next mobster we get, and see how it goes."

"Hey, you could be onto something there," said Liz. "We could sell tickets."

Charlie gave them all an affectionate glare. "I think I'll pass on being stuck in a small room alone with a mobster. But thank you for your resounding votes of confidence, I'm touched."