Don stared in through the window. The medical team that Marker had brought with him had turned the FBI basement into an impromptu hospital, complete with labs and isolation chambers. There were already six victims inside the chamber, and he knew every one of them by face if not by name. Colby was only the latest, the only field agent among the group. All of the others were people who stayed inside the building to perform their function: Marcy, the receptionist. Tom, who worked in the lab doing chemical analysis and who also had an off-color joke to share with people who could appreciate his warped sense of humor. Sara Beth from Translators, fluent in three languages, planning for her wedding sometime next year if her fiancé got home from Iraq. The others he'd passed in the hall on a daily basis.

"Don?" It was Megan.

He knew what she was asking. "I don't know."

Someone pulled the curtain around Colby, presumably to perform some private treatment in some humiliating fashion, trying to maintain the man's dignity as best possible. Don felt savagely glad for that curtain, angry at whoever had done this to a member of his team. To all of his friends here at L.A. headquarters.

"Why him?" Megan asked. "Why him, and not the rest of us? Why not David and I? We were with him almost all day long."

A woman came up behind them, and Don remembered her from his office, as the doctor in charge when Colby took his swan dive. "That's the million dollar question." She waved at the banks of medical equipment inside the glassed in area. "Literally, a million. Maybe closer to a billion. And we still can't figure out what we're dealing with." She stuck out her hand to be shaken. "Dr. Robin Arthur. One of those in there belong to you?"

Don nodded. "Colby Granger. On the end. How's he doing?"

Dr. Arthur grimaced. "I could give you a lot of medical mumbo-jumbo, but the best response is 'as well as can be expected'. We're hydrating him; the biggest challenge with this bug is keeping enough circulating volume in the bloodstream to keep them alive. He's lucky; he's young and healthy and in good condition. Others aren't so lucky. I'm worried about them. All of them, really, if we can't come up with a good treatment protocol."

"Any luck on how he contracted it?" David kept his voice carefully casual.

Dr. Arthur saw straight through him. "Not a clue. We're feeding data into Marker's program as fast as we can, and it spits out garbage. The program's worthless. It's wasting valuable time. We need to find out how this bug is getting into people so that we can break the chain."

"I thought they came up with that answer after Rochester, that it would pinpoint the way the terrorists gotthis stuffinto the building," Don said.

Dr. Arthur snorted. "That what Harrison said? He's an ass. Sometimes I wish someone higher up would see through him." Dr. Arthur folded her arms."Harrison Marker designed his program based on marketing standards, not health care. He studied marketing research for his graduate work, not public health. Nobody knows how he ended up here in Infectious Disease Programs, in a place that he knows nothing of. Somebody sure paid somebody off to get him a job." She looked in through the window at her patients, her mouth curving down in a frown. "You really want to help those people? Help the rest of your friends and keep them from getting this bug, too? Design a study to really identify the transmission and vector patterns. That will allow us to interrupt the cycle and prevent more victims. And, incidentally, lead us to the terrorists. That part is your end of this mess."

Dr. Arthur was frowning, but Don did not. "Doctor," he said, taking her arm. "I think I may have just the person."

"I'm about ready to drive up after him," Don complained. "Hasn't Charlie called in yet? It's three o'clock in the afternoon, for Pete's sake!"

"Not yet." David looked up from his own work, tapping a report into his computer. "He's up in the mountains, Don. Cells don't work all that well in places. He could be pretty far out from civilization. He might have turned his phone off. He'll call in when he gets back. You've already left him six messages."

"You're assuming that he'll check his voice mail. Big assumption, Sinclair," Don grumped. "Anything else come in on the Nelson stuff?"

"Nothing yet. This is boring. His wife can't decide between two crystal patterns at Bloomie's."

"And nerve wracking at the same time," Megan added from her own desk. "I heard a rumor that D'Angelo's administrative assistant collapsed an hour ago. Anybody else hear that?"

"Her, too? I heard about Manny from Maintenance. Left a mess on the third floor women's bathroom."

"I won't go to that floor," Megan promised, no humor in the joke. "I feel like I need to get out of here, out of this building, but don't dare in case something happens."

"And to prevent passing this thing around, in case one of us already has it," Don said grimly. "I know they said that we can't give to anyone else through casual contact, but do they really know? You heard Dr. Arthur. Right now, they're clueless. We're all under orders to limit contact with as much of the public as possible. Just in case."

"How's Colby?" Megan asked. It was a question that each of them had asked almost hourly.

"No change." That too was the hourly response. "He's alive, and not happy, and Dr. Arthur says that's a good sign. And the little beeps keep going off over his head, and she says that another good sign. Something about his heart being regular." Don couldn't help the sigh. There was nothing he could do for Colby, and that was what hurt the most. The man had looked gray through the temporary isolation window, couldn't even summon the energy to do more than open his eyes. Couldn't focus. The last time he'd seen Colby, the agent had been taking down a suspect, flipping him bodily over onto his belly and cuffing his hands. In other words, full of life.

It didn't seem fair.

"I'll flip you for the first shower." Charlie slid the key card through the receptacle, pushing open the door to the motel room and dropping his backpack onto the floor beside the table. He'd briefly considered plopping it onto the chair, and refrained. The backpack had picked up plenty of mud today, and one of them might need that chair for sitting on. The backpack ended up on the floor, as did the mud.

"You're on. Heads." Larry flipped a coin in the air. He too wore the tired expression of a man who'd done the academic equivalent of a full day's work and was well-satisfied with his efforts. "Hah. I win."

"Two out of three."

"No, Dr. Eppes, that was not in the original proposition. I won't be long; I have substantially less hair than you to cleanse. Try not to get mud over everything." Larry disappeared into the bathroom. "And look through the directory," came from behind the closed door. "The sushi bar is terrible, but the Joy Luck makes a wonderful moo goo gai pan."

"Right." Charlie settled back, listening to the water go on with a fairly tuneful tenor gurgling underneath the waterfall. His cell chimed at him, announcing one or more messages, and Charlie winced. He'd forgotten to take it with him, hadn't turned back because they were already two hours hiking up the slope when he'd remembered it. Yes, there were messages, nine of them. Ouch: six from Don. Something must be going on. He skipped through the three from students worried about make up exams due to absences from the flu, and listened to his brother go through various renditions of 'call me immediately' and 'where the hell are you?' and 'what's taking you so long? Can't you put up a piece of expletive deletedequipment and call me back before the sun goes down?'

The sun still hadn't gone down, Charlie thought, punching in his own speed dial. New case? Couldn't have been that terrorist thing; they had that covered, and a good thing. Charlie wouldn't be best pleased at having to deal with that fellow in charge. Don could handle him, though. Don would simply put on those shades of his, stick a wad of chewing gum in his mouth, and stare at the man through the dark lenses and give him the creeps. Don had once told him that staring at someone made them nervous, even if they were innocent of wrongdoing. 'No one is completely innocent,' Don had said. 'Everyone has something they're ashamed of. I just take advantage of the guilt to get what I need and put someone behind bars where they belong.' Ever since then Charlie had developed his own defense when Don or anyone else tried the sunglasses routine on him; he startled doodling with numbers. It got even better when he discovered that it drove Don wild not to be able to get through into Charlie's universe.

Quit dawdling. Charlie hit the call button, wondering what the emergency could possibly be. Whatever it was, it would have to be good. He and Larry needed to hike back up the mountain tomorrow to retrieve the data, come rain or shine or snow. An additional day's delay would cause the data retrieval device to overwrite the information, and the whole project would be ruined. Larry Fleinhardt would not be a happy camper despite having a comfortable bed instead of a sleeping bag.

"Eppes."

"Don?"

"Charlie! Where were you? Never mind; look, how fast can you get back here?"

"Not until at least tomorrow evening." We'll start with that as a working premise until we hear what you have to say, brother mine. Charlie calculated in his head: two hours drive to the parking spot tomorrow, two hours hiking up, an hour to collect the data and dismantle the equipment, only one hour hiking down (taking advantage of gravity, as Larry would observe), two more hours to drive back to town, and then three hours to drive home. "Seven, eight o'clocktomorrow night at the earliest." We'll need to stop somewhere for mundane things such as meals.

"Tomorrow evening? You have to drive back tonight, buddy. We need you now."

Sinking feeling. "What's going on, Don?"

"It's hit."

"What's hit?"

There were times when Charlie could be oblivious to life itself. Don forced down his annoyance. "The terrorist attack, Charlie. We've got people sick." First things first. "I'm assuming you feel fine?"

"Yes. You?" Charlie was now beginning to get a clue, even purchasing a vowel along with it.

"I'm okay, but there are those who are not."

"Okay," Charlie said slowly. "I thought you didn't need me. That Dr. Marker had things under control. He made it very clear—"

Don glanced around to make certain that the door to his office was shut. "Dr. Marker is an idiot. I have that straight from the mouths of his people. The infection transmission computer program that he developed is worthless. We need you, buddy. How soon can you get back, if you started now? I'll even come get you, if Larry needs the car. Where are you?"

"I have a better idea." Charlie pulled his omnipresent laptop out of his overnight bag. "Let me talk to someone intelligent over there, someone who understands the process. I'll create the program here, then email it to your computer. I'll show you how to input the data. That should be faster than me trying to get home." With the added advantage of not disappointing Larry.

With the added advantage of not exposing Charlie to this bug, was Don's own thought. "That sounds good, buddy. Don't go away. I'm going to get Dr. Arthur to talk to you, explain what she needs to find out, and I'll leave you two to go at it." He handed his cell to Megan. "Don't let him get off that phone. We'll never get him back."

It took Don only three minutes to get down to the basement/medical center but another six to pull Dr. Arthur away from her duties. Don couldn't resist another look at Colby. The man was sleeping on his cot, a light cover over him. Even from this distance Don could see lines pulling down at Colby's face. Not one but two IV's were hanging, dripping in life-sustaining fluids. "How is he?"

Dr. Arthur thinned her lips. "In a lot of discomfort. I've given him something to help him sleep through it, as much as I dare. Cholera—in this form—causes intense abdominal cramping, among its other myriad of pleasant symptoms. Try to avoid getting it, Mr. Eppes," she added dryly.

"That's what I'm here for, Dr. Arthur." Don explained his plan.

Dr. Arthur got a small glimmer of hope. "Your brother thinks he can devise a computer program to determine the vector of this thing? How it's getting to the victims?" she translated.

"Worth a shot," Don replied. "You've already said that Marker's program isn't worth squat. Want to give Charlie a try?"

Dr. Arthur headed for the elevator. She hesitated, waiting for the elevator to arrive. She turned to Don. "Your brother wouldn't happen to be Charles Eppes, the mathematician?"

"The very same. You've heard of him?"

"I double-majored in math and physics as an undergrad. Yes, I've heard of him."

"That's a first. Usually people's eyes look blank."

"Like Marker's?"

"I wasn't going to name any names."

"Huh. Marker really is a fool," she said, stepping onto the lift. "I'd like to meet your brother."

"Dr. Arthur, I'll make certain that you get that opportunity."

Don tapped the button that activated the speaker phone. "Charlie? Still there?"

"Been here for the last ten minutes."

"What's the matter? Don't like talking to Megan?"

"I love talking to Megan, but I'd rather get moving on this program. Larry will be out of the shower soon, and I need to get in. It was a long hike. I stink."

"Tell Larry to use a clothes pin. I've got the job for you, buddy. Listen, Dr. Arthur is here with me. She's the doc on this mission."

"Hi, doc."

"Call me Robin," she replied, leaning over to make sure that she would be heard. "Are you really Dr. Charles Eppes?"

"My friends call me Charlie. What can I do for you, Robin?"

And they were off. The parameters flew back and forth: the characteristics of Cholera, how it got transmitted from one person to another, the life cycle of the lowly bacterium. Don and the others tried to keep up. They learned that an inanimate object that carries the bacteria is called a fomite, and that the primary treatment of the patient was to pour water and electrolytes back in as fast as the victim lost it. People with blood types A, B, and AB tended to be immune, while those with O the most susceptible. The incubation period of normal Cholera was one to five days, but this current mutated variety had already been demonstrated to incubate in two days or less and while victims usually consumed the normal bacteria through contaminated water, the method of transmission of this mutated variety was less clear cut. Robin Arthur did most of the talking.

Then it was Charlie's turn. His needs were data collection; there was a link between all of the victims, and it would take a lot of sifting to find it. He talked about office location, eating habits, chewing on pencil habits, and things so extraneous to what Don thought should be important that Don lost all track of the entire process.

Then they were done. Or so he thought.

"E-mail isn't going to work, Don."

Uh-oh. "Then I'll come and get you. Get your stuff together, buddy. I'll hit the lights and sirens—"

"Got a better plan, Don. We'll slave your computer to mine. Better call your computer people. I could probably do it myself, but it would take forever to get past the security protocols, and then your people would be terrified that I'm an agent of a foreign power and cut off the transmission in the middle. We're going to hook up your computer to mine through the internet, and I'll put together what Robin needs."

"I like that idea a whole lot better."

It only took fifteen minutes for the computer whiz from the FBI's IT department to confer and confabulate with the math whiz.

Don was always alternately amazed and spooked when the cursor on his computer screen took on a life of its own. The cursor zipped around the screen, hunting for the programs that Charlie wanted.

Charlie finally hung up his cell, concentrating on his laptop at the other end, promising to call back once he'd completed his portion. Screens came and went, flying through data analysis, setting up equations and verbal questions leading to those equations. Robin Arthur looked on in rapt amazement, murmuring to herself and occasionally letting out an 'oh, yes, now I see," but more frequently a 'how did he get there?'

"Don't let it bother you," Megan told her. "You get used to it. Just sit back, and let Charlie hand you the results."

The changing screens slowed to a stop, and Don's phone rang again. "Eppes."

"Don? I got—"

"Let me put you on speaker phone, buddy. There. Hear me okay?"

"Yes. Everybody there? Robin?"

"Right here, Charlie. You've finished it?"

"I've finished the program," he affirmed. "It's a down and dirty mess, but it should get the job done. All you have to do is enter the data on each of the six patients. I've made it open-ended, so you can add more patients as they arrive. I'll crunch the data results tomorrow morning if it's ready, or tomorrow afternoon if it isn't. It will probably be tomorrow afternoon. There's a lot of data to be both entered and correlated. Got it?"

"Got it," Robin nodded. "Thanks, Charlie. Looking forward to meeting you in person. Nice work."