Disclaimer in Part 1. Thanks again to Becky for beta reading and to Lady Shelley for maintaining "Running the NUMB3RS."

It's always so sad to post the last chapter. --sniff-- Thanks to everyone for reading, and special thanks to my faithful reviewers; you make it all worthwhile!

ooooooooooooooooo

Chapter 14
Thursday, December 1, 2005
7:55 P.M.
Eppes house

Charlie flung open the front door. "Dad?" he called out anxiously.

"Yes?" came the reply from the living room.

"Is everything okay? The car's gone from outside." Charlie's heart had leapt into his throat after he had steered his bike into the driveway and noticed the anomalous condition of the street in front of their house. It had only taken a day or so for him to get used to the unmarked police vehicle being there, so its current absence was more than a little alarming.

"Everything's fine, Charlie." Don's voice came from the couch, out of his line of sight. "We caught the last guy we were looking for this morning, so we sent the cops home."

"Oh." Relieved, Charlie let his backpack slide off his shoulder. "That's great news," he said as he stepped forward and shut the door.

The new rug in the foyer was something he was not yet used to, and he stumbled a bit as his feet contacted its edge. A few days earlier, once the house was no longer officially a crime scene, they had found that not even a strong ammonia solution would remove all of the bloodstains from the wood floor. So he and Alan had decided that a new floor rug was a better solution than tearing up the floorboards and finding planks to match, at least in the short term.

But the out-of-place rug made it hard to look at the floor in that room without picturing a dead man lying on it, even if he hadn't actually seen the corpse. And after hearing the story of what had happened there, from both his father's and brother's points of view, it was even harder not to picture one of them in that spot.

He shook his head to clear it and glanced at his father, who was gazing over his Sudoku book at him with that look that usually meant he knew exactly what was running through his son's head. "Yes, it is good news," was all he said in reply.

"So, um, did Stan's tip pay off then?" He took a few steps forward into the living room, turning his back on the foyer.

"Yes, it did," Alan replied. "Can you believe that? Here I am on the guy's case about being overly enthusiastic in finding us work, and he ends up leading the FBI to two terrorists."

"Not more clients of yours?" he asked.

"No, no, although Stan wanted them to be. Ellen Basso had mentioned that her British friend had some associates up in Oakland, and Stan wheedled a couple of names out of her, thinking a little work in the Bay Area would be good for our reputation." He sighed. "Some reputation that would have been."

Charlie gave him a concerned look. "You don't think your business is going to suffer because of this, do you?"

Alan gave a deeper sigh. "Let's just say we're going to stick to housing and retail projects and nothing that could do any damage if it fell into the wrong hands."

"At least as far as you know," he said darkly, thinking of a young computer genius throwing questions at him about knowledge and responsibility that he had never been able to satisfactorily answer for himself, even all these months later.

"Well, your brother has stopped threatening to do a background check on every client who hires us, but I can't say I blame him." Alan dropped the puzzle book into his lap. "When I think about what might have happened…"

He couldn't help his gaze shifting to the spot on the floor that he knew was there, underneath the carpet. When he looked back at his father, he was shaking his head. "Not that. I've been trying as hard as I can not to think about that." When Charlie nodded, he went on, "But what might have happened if the FBI hadn't figured out that something was going on. If these guys had been able to get something into the water supply…" He trailed off again and shook his head.

Charlie took a few steps into the living room and dropped onto the couch next to Don, setting his backpack down on the floor. "But according to my model, it would have taken a considerable amount of any kind of contaminant to get all the way through the aquifer. Most of the substances stored at JPL aren't as water soluble as perchlorate, so you would need even higher quantities of anything else."

"He's not talking about chemicals stored at JPL, Charlie. He's talking about anything you can think of putting in the water supply." Don broke his silence and set his empty beer bottle down on the coffee table. "Ellen Basso might have had some harmless little stunt in mind, but those other guys sure didn't."

As the words sunk in, Charlie was glad he was sitting down. His thoughts over the past few days had been so occupied with the personal danger to his father and brother that he hadn't really focused on the other ramifications of Mott and Andina's actions. Don's left arm would be in a sling for a little while yet, and while their father was convinced that Don had driven himself too hard the night he was shot, Don insisted that the bullet hadn't done much more than scrape the surface. Charlie didn't know which one of them was right, and he had tried not to think too closely about it.

But now his mind started racing, calculating the likely dispersal rates of arsenic or cyanide or various biological agents. He briefly closed his eyes, then opened them to find both his father and brother looking at him. "Did you find out anything specific from your suspects?" he asked Don in a low tone.

"Not yet. Apparently they didn't have time to get all of the details of their plan in place. The no-fly list guys were bringing in the technical expertise, and Andina and Mott were supposed to be responsible for getting the materials."

Alan broke in from across the room. "And apparently what those materials were was going to depend on what I told them, or at least what I told the Bassos." His expression looked as haunted as Charlie could ever remember seeing it.

"Dad, it's not your fault," Don began in a tone that indicated they'd already had this conversation, but Alan waved him off.

"I know that," he said, tapping the side of his head. "At least, this part of me knows it. It's the emotional side that's going to take a little more convincing."

Now that was something, ironically enough, that the mathematician could relate to just fine. But something else was bothering him. "Can you explain something to me, Dad? I don't know how the two of you can sit here, right where—" Charlie broke off and gestured towards the foyer. "I mean, I wasn't even here when it happened, and I'm freaked out by the thought of being here. I don't know how you can do it."

"I figured there was some reason you'd been spending so much time at your office this week," Alan said knowingly. At Charlie's rueful smile, he went on, "Well, for one, I live here. I don't want to feel like I'm being chased out of my own home. On the other hand, it's not like I really have anywhere else to go." Nodding towards Don, he said, "And it seems sometimes like your brother doesn't have anywhere else to go, either."

"Hey, is it a problem if I like the company of my family?" Don's voice sounded slightly injured.

"Not as long as you take us out once in a while to compensate for all of the dinners you mooch off of us," Charlie teased.

Don shot him a look in reply, but didn't say anything.

"To answer your question, Charlie, different people have different reactions to stressful situations," Alan went on. "This is actually the first evening I've been able to sit here for more than a few minutes without my mind going over and over what happened." His gaze shifted to Don, and something passed between the two of them that Charlie couldn't read.

Knowing what had happened between them, though, he thought he could guess. He'd watched both of them being debriefed, and he was getting a little better at reading between the seemingly unemotional lines of his brother's professional façade. The two of them had risked their lives for each other, and he supposed that that forged a bond that you had to be part of to understand.

And he hoped he never found out what that was like firsthand.

Alan continued, "I know it's going to take a while, and that little things are going to keep bringing it back up to the surface, like when the doorbell rang last night with the pizza delivery." He shook his head. "I knew the cop out front had cleared him to come in, but I still almost made him leave it on the front step without opening the door. But it'll get better." He looked over his glasses at Charlie. "I suppose that's what being older gets you. Lots of experience in working through trauma."

Charlie quirked up the corner of his mouth and looked away. That was one area of his life where he definitely didn't want any more experience. He turned towards Don, and the expression on his face told him he was thinking the same thing.

Something else occurred to him, and he looked back at his father. "So, um, did the city say they would be able to take back those files?"

"Yes, thank God." Alan took off his glasses and laid them on the end table. "Ron was more than willing to find room for them in a more secure location once he heard what happened, and I am more than willing to let them go. He's going to send somebody by tomorrow to pick them up."

"Good." Charlie rubbed his palms on the outsides of his legs. "'Because I was looking up in the attic again, and with those boxes out of the way, and what we managed to sort through last time, I think I'm satisfied that there's not a fire hazard anymore. So we don't need to, um, go through anything else up there." He paused and added quickly, "Unless you want to, that is."

Alan was regarding him shrewdly. "No, I think if you're satisfied, then that's enough."

There was a momentary silence. "'Cause you're right, you know." Charlie fidgeted with the seam of his jeans as he went on. "Everyone needs to work through their trauma in a different way."

Another pause. "Sure thing, Dr. Phil," Don finally said, elbowing him in the side.

He instinctively responded with an elbow of his own, and soon the brothers were mock-tussling on the couch, Don as best he could with only one arm, ruffling hair and jabbing shoulders. Then, "Boys, knock it off," Alan commanded in an all-too-familiar tone.

Charlie instantly straightened up, and beside him, Don did the same. He opened his mouth to say, "He started it," and then the absurdity of the situation struck him and he couldn't suppress a huge grin. Beside him, Don was quietly sniggering under his breath.

"The more things change," Alan said, putting his glasses back on and returning to his Sudoku book.

He looked sideways at Don, who was still chuckling a little. Out of the corner of his eye, he could see the streetlights coming on, chasing away the deepening twilight with a soft orange glow. The dark blue color of the sky made him think of something, and he reached down into the backpack sitting at his feet and pulled out a foil-wrapped tube of candy left over from this morning's class. "Life Saver?" he asked, proffering the roll towards Don.

"Yeah, sure." Don accepted the roll and plucked out a round white-and-green disc. "Here, Pop," he said, tossing the roll at Alan. "Hey, these are the wintergreen ones, right? The kind that glow in the dark when you chew on them?"

"They give off sparks, right. It's actually a phenomenon called triboluminescence, the generation of light when the asymmetrical bonds in a crystal are broken." He held up the piece of candy for them to see. "The crushing of the sugar crystal creates a very small electrical field, and like with a bolt of lightning, a spark occurs when the positive and negative charges reunite. There's even a tiny bit of nitrogen emitted, same as in a lightning strike."

"And what does this have to do with anything, Charlie?" Don's tone was a mixture of amusement and tolerance. He could remember a time when that question would have been asked with more impatience or frustration than anything else. Some things might stay the same, but other things very definitely did change.

"It was something I explained in my applied mathematics class today, about asymmetry in crystals and how the application of force can produce unexpected effects. The wintergreen oil in the candy is actually luminescent itself, so it absorbs the UV wavelengths emitted by the breaking of the sugar bonds and briefly flashes blue."

"Uh huh." Don clapped him on the shoulder. "So did you turn out the lights in your classroom so everyone could see the sparks?"

"The classroom blinds won't close all the way, but I did suggest everyone try it at home." He jerked his head sideways, indicating the direction to the stairs. "I think the bathroom upstairs is dark enough. Let your eyes adjust for several minutes before you try it."

"How long?" Alan asked, surprising him as he laid aside his puzzle book and rose to his feet.

"Five minutes or so is best."

"I don't think there's room enough in there for both of us, Pop. Let me know what happens, okay?" Don leaned back against the couch and bit down on the piece of candy.

"You don't believe your brother?" Alan shook his head and pulled another Life Saver out of the package before handing it back to Charlie. "What did you call this again? Tri-oh-what?"

"Triboluminescence. From the Greek word tribein, to rub. Because it's the friction created by the breaking of the bonds that leads to the light being made."

Alan held up the small white disc. "I'll report back in a few minutes."

As Charlie watched his father walk away, his gaze swept around the familiar room, going from the new rug on the floor, to Alan's back as he retreated towards the stairs, to the host of family pictures on the walls, and finally to his brother, sitting beside him.

It was a weak metaphor, and he could imagine Larry taking him to task for it. But it had struck him so powerfully a moment ago: he could almost see the triboluminescence in this room. Not from the candy he was crunching between his teeth, but from the three people here in their mutual home. It didn't matter what darkness might enter their lives and threaten to break the bonds between them. Together they could create enough light to chase it away.