An hour later, pretending not to be shaken from their close call--still got work to do here, guy!--Don and Megan walked into the lecture hall to find Charlie winding down his lecture for the day. His brother had his back to them, jotting something incomprehensible to ordinary mortals onto the whiteboard, adding underlining for emphasis. He turned back around. "So what this means, for those of us who are expecting the homework to be done, is that you can use these equations to determine the probability of event A occurring over the probability of event B. To further explain, the probability of receiving an 'A' for this course is substantially greater for turning in the solutions to the even-numbered problems than it is for turning in the solutions to the odd-numbered problems at the end of chapter four. And by 'turning in the solutions' I do mean show-your-work. Answers only will get minimal credit only."

"But Prof. Eppes," one young girl wailed, "we can't check our work if you want the even-numbered problems. How do we know if we've gotten the right answers?"

"You're right," Charlie told her, and the rest of the class. "However, you have just earned bonus points for reading ahead and realizing that the odd-numbered problems have the answers at the end of the text. Collaborative work is not only permitted, but encouraged," he finished, dismissing the class. "There is strength in numbers, pun intended. Hi, guys," he greeted Don and Megan as they approached. "What's up?"

Then Charlie wrinkled up his nose. "Don, I hate to tell you this, but you should shower after working out. I thought my class tried to escape a little early."

Don's answering smile was tight. "Tends to happen when somebody tries to kill you."

"What?"

"Everyone's okay," Megan soothed, throwing a significant glance Don's way. "Nobody got hurt. Just a few feathers ruffled."

Charlie eyed the pair of them, not convinced and more than a little upset. "This assassination attempt have anything to do with the exploding paperweight thing you asked me to look at the other day?"

"Probably not." I'm not lying to my brother, Don told himself. It could be any one of a half dozen cases that I've closed recently, that are going to trial. "Anyway, it's over. But you're right, we need your help."

"Talk." Charlie perched on the edge of the desk.

"Got better than that. It's show and tell time, Professor Eppes." Don pulled out a copy of the paper that had arrived in the letter that David and Colby had found. "Ever seen anything like this?"

Charlie's face froze. "Where did you get this?"

"Then you do recognize it."

Charlie stared at the paper for several long moments. Don, mindful of Megan's silent urging behind him, kept still for as long as it took. But I'm not leaving here without some answers, brother mine.

"Charlie?" To Don's satisfaction, it was Megan's nerve that broke first. Her voice was the one to try to recall the mathematician to reality.

Charlie wasn't even looking at the paper any longer. He was staring off into the distance, squeezing the paper into his hand as though to absorb the information written onto it directly into his flesh.

"Is this what got Ned Ames killed?"

"We think so." Megan moved in, put a sympathetic hand on Charlie's shoulder. Don envied her ability to touch people not just physically but emotionally. Right now it was what would get Charlie to open up, to tell them what they needed to know to solve this murder.

But Megan shook her head imperceptibly at Don: not yet. Don swallowed his impatience, waited for Megan to work her magic.

Silence. Therapeutic silence, Megan would call it. The ability to wait, to keep quiet until the witness—in this case, the expert consultant—was ready to talk.

Charlie finally sighed, slumping onto the desk. He fingered an ancient pen mark etched into the wood of the desk, the ink long since faded. "I worked with Ned four, almost five years ago. He was a bright guy. I used to think that he'd end up teaching math somewhere, after he retired from the NSA. I kept telling him that I'd give him a reference when he was ready to get into a real line of work."

"You worked closely with him?" That was a given. What Megan was doing was encouraging Don's brother to keep talking.

"Not all that closely. I met him twice, in person. Mostly we 'talked' over the internet, on a secure line. But I taught him how to encrypt this sort of information, taught him how to create an almost unbreakable code."

"Almost unbreakable?"

Charlie's smile was positively anemic. "There's no such thing as an unbreakable code, Megan." He seemed to have forgotten that Don was even there.

"And you taught him."

"I taught him." Charlie looked at the whiteboard as if it was reminding him of something. "I developed the key that he used when sending back information from where ever he was stationed. I taught him what he needed so that he could get himself killed." Bitterly.

It was time to bring Charlie back to reality. Don cleared his throat. "Do you know what this paper says?"

Charlie blinked. "What it says? No, not yet. It's in code. Goa'uld, actually, is what we called it." Another weak smile. "That's what Ned called it. He was a SciFi buff, loved some of the television series. There was this really neat one that he showed me, a sixties SF comedy about a space-faring garbage scow." He sighed, bringing himself back on task this time. "His nick name was Ned 'Take Aim' Ames. He was also a dead-on marksman. Held a few records somewhere, I'd heard." Charlie looked away. "And now you have him, dead, lying on some pallet in a morgue."

"You liked him." Megan kept Charlie talking, wouldn't let him stop.

"It's hard to like someone at the other end of a code line, but those of us back at NSA headquarters would get a real feel for people at the other end. You start to know how they think, how they put stuff into code. You get to know them, in a strange sort of way." He looked away.

"And you knew Ned Ames."

"Yeah." Charlie gave a short laugh. There was nothing funny about it. "As much as anybody who consults knows a field agent." He set his lips. "Give me the paper, Don. I'll go to my office. I'll find out what Ned was trying to tell us. It'll take me a hell of a long time, but I'll decode the damn thing and find out what was important enough to get Ned killed."

"Again, symbols." Charlie traced the coded message onto the whiteboard in his office. "It's what math is: symbols. A symbol for one, a symbol for 'A', all of which make up communication. Oriental languages can use pictographs, but the Western tongues use symbols to represent sounds. Or numbers, which then go on to represent quantities. Here we have those symbols scrambled into various different systems. As in any equation, step one is to reduce the format of all the symbols into a single system; in this case, English. Some of this is easy. The Greek letters have clear analogs in English." At this point Charlie was more talking to himself, but Don didn't mind. Charlie was pulling off his magic, and that was what was important.

"The Cyrillic, the Russian alphabet, again is relatively straightforward. Here Ned uses only the symbols that are common to English, although one has to be aware of the differences that some letters have. The 'C' for example, sounds like an 'S' and is never a 'K'. And the 'P' is really an 'R'. This lower case n transliterates into a 't'. And so forth, and so on." Charlie jotted notations below some of the symbols. "It's when you get into the Arabic and the Hebrew that it becomes complex. One needs to know the sound of the symbol in order to be able to transliterate it into the English sound, and from there into the appropriate symbol. Then the hard work begins." He looked up at Don and Megan, breaking off his own lecture. "Don, this is going to take a while. I can probably finish this first part in a couple of hours, setting in the probabilities for some of the more challenging transliterations. But without the key to the code, I'm fishing in the dark. This could take days to figure out; more likely weeks."

That gnawing pit of the stomach sensation grew. Don narrowed his eyes. "But you can do it, right?" Got a lot riding on you, Charlie.

"Yes. Eventually. But Don, I need that key," Charlie repeated. "Ned was very very good at encoding his information. Think of those little decoder rings that we used to get in cereal boxes. You could only see the information after you ran it through the decoder ring. Ned's key is like that. I have the message, but half of it is garbage, and I won't know which half until I run it through the decoder ring, otherwise known as the key. After I get this first part decrypted, I could get the message decoded within half a day at most. With the key, that means," he added. "Without it?"

"Without it? How long?" As in, maybe the key got shattered in the explosion and doesn't exist anymore?

"Days. Maybe a couple of weeks, working full time on it. This is complex stuff, Don," Charlie said. "Cutting edge, cipher-wise. There's a reason that the NSA puts so much money into its code work. We're not talking a simple decoder ring here, Don. We're talking a process that I spent most of six months developing."

Don winced. "That bad?"

"But, Charlie," Megan objected, "if you developed it, can't you figure it out? I mean, this is your system."

Crooked smile. "Megan, this is the NSA. Your consultant develops a communication mode, then goes back to civilian life. For the most part," Charlie added, holding up a finger to forestall any objections. "The occasional FBI consulting job not withstanding. Wouldn't you want to make a few alterations? Just so that consultant couldn't be tempted by a few million to divulge the secrets?"

"Charlie, you wouldn't do that," Megan said. "You're too honest."

"Too honest for your own good sometimes," Don added wryly.

Charlie shrugged. "Let's just say that I did get a few offers, a short time after I left. I'm pretty sure that one of 'em was a set up, to see what I would do, but a couple of the others?" He sniffed, remembering, grinning. "You might have had to jet down to my own private island for a consultation, with what they were offering."

"That much?"

"More. Enough to buy Dad his own separate island as well. And it would be my jet."

"Ouch." Don rubbed his hip pocket, where he kept his wallet. "I think I'd better talk to Accounting, tell them to up your consulting fees. Wouldn't want the competition to steal you away from me."

Charlie shook his head. "Don't bother. Strictly on price, you couldn't afford to match what the private or another governmental sector has offered."

"Which means we give you something better." Megan was on the ball.

"Yeah." Charlie's face lit up. "How often does a math professor get to talk about solving a murder?" He turned to jot something onto the whiteboard.

Bang!

The window shattered, courtesy of a small metal object fired from a long-barreled rifle. The bullet drilled straight into the Hebrew aleph on the whiteboard. The aleph was located a mere three inches above Charlie's shoulder.

No time for thought: Don reacted. Charlie, the civilian, was closest; Don grabbed his brother by the shirt and threw him to the floor of the office. Charlie let out a yelp of surprise. Don scuttled to the window, handgun in his fist, peering out. Dammit, this is twice in one day!

Megan was already there, her own gun in her hand, her cell phone in the other. "Shots fired," she reported, her voice terse, giving the location of Charlie's office. "Everybody okay?"

"Good, here."

"Fine." Charlie's voice held a suppressed tremor.

Don spared him a look, then did a double take. "Charlie, you're bleeding! Where did you get hit?"

"I am?" Charlie dabbed at his head, brought his hand down with blood over it. He blinked, and paled.

"Don't move," Don instructed. Dammit, where was back up? He was going to have a word with whoever. Second time today they'd been shot at! What was this, pick on the FBI week? "Megan? You see anybody?"

"I think they've gone." Megan peered out through the shattered window, daring to lift her head a little higher above the sill. When no shots arrived to muss her hair, she crawled back to her feet. "I think that's a definite. They're gone."

Don too surveyed the outside scene. There were still students walking around as if nothing had happened. For them, nothing had. They hadn't even heard anything out of the ordinary, just the sound of a car back-firing and with all the barely running vehicles that students had, the sound of a back-fire was no big deal.

The shooter was gone. Don assessed the possible locations: judging by the angle of the shot, it would be someplace high up, say across the courtyard from that other classroom building there. Yes, there was an open window just one floor up compared to right here. Don marked that in his memory for an investigation. They'd dust it for fingerprints, but, with the professionalism of this attempted hit, he doubted that they'd get any.

He turned back to more important things. "Charlie?"

Charlie blinked, wiping away the blood running into his eye. "I don't understand. It doesn't hurt."

"It will," Megan promised. She held a wad of tissues to the spot on his forehead, applying pressure. "I think you got nicked by a ricochet. Just sit right there. The paramedics should be here in a moment."

"What happened?"

"Somebody shot at us," Don said grimly. "They tried to take us out on the way here, and now this." And my brother almost got in their way. He looked back at Megan. "It's either you or me, kid. Which one of us is someone trying to off?"

"More importantly," Megan asked, "why?"

Colby ambled back into Charlie's office with a gait that said relaxed to outsiders. Don knew better. There was a tension in the agent's gait that spoke of nerves stretched to high-wire tautness, ready for action, reflexes honed under combat conditions. Which these were, Don reflected. Nothing like getting shot at to make a man sweat. Don was stinking even to himself at this point.

"A few shells left, Don," Colby reported. "Just enough to tell us that someone was there. It was pretty obvious; they didn't bother to cover anything up that they didn't want to. It was a professional job. No prints, some smudges where someone set down the case that they brought the rifle in with. The bullets say something like a high-powered sniper special, maybe a modification or two. I've got Forensics on it, trying to track down exactly which type of weapon. Maybe we can get a clue off of that."

Don frowned. "No leads as to who they were from?"

"Nope."

"I've pulled all of your recent case files," David told him, "yours and Megan's, which are pretty much the same ones. There are a couple of people coming up that wouldn't mind seeing the both of you not capable of testifying against them but, Don, none of them really look good for this. One case is that bank fraud that might go either way even with your testimony and the other has a history of non-violence."

"Yeah. I remember. That guy that always tipped his hat on his way out of a job." Don grimaced. "Keep at it. Getting shot at comes with the territory, but I'm not real thrilled with innocent bystanders getting hurt." He looked over at his brother. The mathematician was sitting in his chair, the seat swiveled away from the desk so that the paramedic could apply a clean white dressing over the wound on his head. Better; Charlie didn't look quite so pale. "Charlie?"

"You stink," Charlie informed him, "and I'm not talking about that time you pounded me after that baseball game that you lost when I was seven. You stink even worse than you did earlier today. Take a shower."

Don chuckled. "I take it this means that you're all right."

"No, I'm not all right. I have a head ache the size of Larry's cyclotron, computer room included."

Yeah, but that's a good thing, Don wanted to tell him. You're alive. "Colby, take him home, okay? There's no concussion, right?"

"No concussion," Charlie put in irritably before the paramedic could say anything. "Although you wouldn't know it from the way I feel. And, anyway, I'm staying right here."

"Huh?" Was Charlie nuts?

"I have the things that I need to crack that code here in my office, not at home," Charlie informed him. "I'm staying."

Certifiably, completely nuts. "Charlie," Don said patiently, "you just got your head bounced by a bullet. In my book, that entitles you to go home and rest. The code can wait another day." I hope.

Charlie hit him with the big one. "This means that I have to tell Dad what happened. I get to listen to him yell at you."

Ouch. Don steeled himself. Consultant or no, Charlie had to go home to rest. And the Forensics team still needed to sweep this office, and for that they needed Charlie out of the way. All of which meant that Don needed to stand up and take his punishment like a man. "He'll find out, anyway. Better to let him know now. Then he can shoot me himself."

Colby inserted himself with a move for which Don knew he would have to thank the agent sometime in the near future. "C'mon, Charlie. I'm taking you home. No more arguments. You won't be able to work with your head pounding, anyway." He took Charlie's elbow, lifting the mathematician firmly out of the chair and toward the door, not taking no for an answer.

"I'm taking the paper with me," Charlie protested. "Wait! I need that book, too. No, not that one! That one!"

Fine. Don handed him the text without a murmur. At least Charlie wasn't trying to stay here any longer. "Not a problem." Don gave in easily. Two minutes of trying to work, and Charlie would fall asleep on the sofa at home. Don could live with that. "Just don't let anyone else see the paper, okay? This is national security, remember," he said. "NSA? CIA? A bunch of other alphabet soup agencies, remember?"

"I remember," Charlie said, cranky. Don knew that tone. It was the same one Charlie had used when Mom made him put his math books away when he was too tired to see straight.

He grinned at the memory. "Go home, Charlie. I'll check up on you later. After I get your office cleaned up." He looked around, seeing the stacks of papers that had floated to the floor in the wake of the bullet and the activity that followed. "Maybe just some of your office. The rest is your problem."

Colby kept his car moving smoothly through traffic. There were only a few cars in the area despite—or perhaps because of—the afternoon hour. Kids weren't out of school yet and the hookers weren't out of bed yet. The only people on the streets were the independently wealthy types and those for whom employment meant going hither and yon in a car for a living. He glanced at the man beside him; Charlie had closed his eyes, though he didn't appear to be sleeping.

He wasn't. Without opening his eyes, Charlie said, "you will watch out for my brother?"

Quiet chuckle. "You got it, Charlie."

"Who's after him?"

"Aren't you supposed to be resting? Isn't that why I'm taking you home?"

"Answer the question, Colby." Charlie cracked one eye open. He winced at the bright sunlight, but determinedly kept it open. "This is my brother we're talking about."

"Who was been successfully looking out for himself for the past several years, including the wild wild west of New Mexico. I think he can handle himself, Charlie."

"Yes, but—hey!" Charlie sat up, both eyes open.

"Charlie?"

"That symbol! It's the Goa'uld symbol for naquedah!"

"You lost me there, buddy."

Charlie stared straight ahead, both eyes open now, seeing nothing. "I couldn't figure out what language that last symbol was, and it just came to me! It's the Goa'uld symbol for naquedah. It's part of the message that Ned sent. It stands for nothing in real life. Therefore, the message refers to enriched uranium. Weapons-grade uranium. That's part of the key, Colby!" He got excited. "Hurry up. I need to write this down!"

"Use some paper. There's some on the back seat. How did you get from a TV show to radioactive weapons?"

Charlie started to shake his head, then thought better of it. "Naquedah is a power source that goes boom in fiction. Anyone who knew Ned would know that. That's the key to the key."

"The key to the key. You've lost me."

Charlie chuckled, a welcome sound to Colby's ear. "That's okay. You just tell Don when you see him that the FBI should be concentrating on that angle. Somewhere, somehow, nuclear weapons will be involved. Information on who's buying what and where, that sort of thing."

"That makes sense," Colby mused. "If this Ned guy was doing intelligence in the Middle East, that would be an important angle to send back home. Even worth killing over."

"Which brings us back to my brother. What's going on with that, Colby? Somebody shot at him and Megan twice today."

"And missed both times," Colby replied.

"Third time's the charm."

"I thought you weren't superstitious."

"I'm not, and don't change the subject. I'm referring to statistical probabilities over time. Who's after my brother?"

Colby got serious, knowing that it was the only way to satisfy the passenger in his car. "We don't know. There are several possibilities."

"None of whom look good for this. I heard you in my office."

"Then you know as much as I do," Colby told him firmly. "Don's made a lot of enemies over the years. It's natural, especially for an FBI agent of his caliber. We're following up on it. Let it rest, Charlie. Go home, sleep off your headache, and then solve the code. That's how you can help Don." His voice trailed off, concentrating on traffic. There was that large black sedan up ahead, driving too slowly for road conditions. Maybe looking for a house number…

Bang!

Someone rear-ended them, shoving them forward into the sedan ahead. Backward motion jolted into thrown forward as the front end of Colby's car connected with the object in front. Air bags deployed with another bang, deflating as quickly as they'd opened. Charlie yelped in shock.

Damn rotten timing for a car accident—

No accident. The ramming from behind was deliberate; the automatic weapon pointing through the shattered windshield was evidence of that, as were the faces covered with black ski masks. Colby's instinctive move toward his own gun stopped. Death was very close.

"Smart," one masked figure growled. "Get him." He gestured to the other side of the car.

Another masked figure yanked Charlie out of the car, leaving the car door open. He staggered, and another masked gunman grabbed his arm. The two of them hustled the mathematician to the forward sedan, shoving him inside.

"Don't come after us." The masked gunman aimed.

Colby ducked below the dash. Bullets sprayed across the seat where he'd just been sitting. The next round took out both the radiator in the car and the front tires. Seconds later he heard the roar of a powerful sedan engine taking off into the distance.

He darted out of the car, trying to see the license plate.

Too far away.

Colby slammed his hand down on the hood of his ruined car. Sweat poured off of him as the adrenalin seeped away, his pulse deciding that it no longer needed to race. Death had come this close.

Colby straightened unhappily and pulled out his cell phone. He sternly told his hand to stop shaking with after-shock, and grimaced. After this, Don wasn't the only one who needed a shower.