"I can walk," Charlie complained, trying to open the back seat door to the Suburban. Don turned the engine off, pocketing the keys and turning around to talk to his brother.

As always, the house brought back memories of growing up. Of baseball, and skinned knees, and a myriad of special tutors for Charlie. Even a broken arm, once. But it was Charlie's house now, purchased from their father. Funny, it still felt like Dad's house. He knew that Charlie felt the same way, always asked their father for permission before making changes. Drawback to inheritance. Charlie reached over the seat. "Give me the crutches."

"Not a chance," Don grunted, hustling out of the driver's seat to prevent his younger brother from hauling himself out of the Suburban, casted leg first. "Stay right where you are."

"I can take care of myself. They discharged me from the hospital," Charlie pointed out.

"Which doesn't mean that you're ready to charge back to work," Don told him in no uncertain terms, scanning the surrounding neighborhood. "Give me your arm."

"I can use the crutches," Charlie insisted. "I can walk."

"Not fast enough." David slid into the argument, and slid into the other side of Charlie, draping the mathematician's other arm across his shoulders instead of handing him his crutches. "Charlie, we received a picture of you targeted with a sniper's rifle. We're minimizing exposure time by hustling you from the protection of the car to the protection of inside. This is my ass we're protecting, as well as yours and Don's."

"Oh." That put it in a whole new light, and made sense. Of course it made sense; it had numbers. Don wondered if Charlie was estimating the 'percent reduction in travel time from the driveway to the front door that resulted by accepting help instead of using the independent but slower crutches'. Probably was; there was a certain amount of sheer insanity associated with genius, and his brother seemed to have his full share of both. "Okay."

"That's it? Okay? No more arguing?" Annoyance; Charlie would listen to David but not to Don, the senior agent? And Charlie thought Don was pushing the sibling rivalry thing.

"Donnie? You got him? Bring him inside. You want him to catch pneumonia?" despite being a balmy seventy degrees outside. Alan Eppes came to the front door—and out onto the stoop. "Let me give you a hand." Still miffed at being told to come home and wait for Don to bring Charlie home. Alan had wanted to wait and escort his youngest home himself.

"Dad!" Don shouted, suddenly more scared. "Get back into the house! Taylor!" he yelled, calling for the guard that he'd had sent ahead. What was his father doing, coming out to present another target for a sniper? Was his father as crazy as Charlie? Had neither learned nothing all the years that Don was with the FBI?

But Taylor, an overly large and stocky man with—most important—a bullet-proof vest, hustled out and covered his father, shoving the man back inside the house within seconds. Don breathed a sigh of relief and returned his attention to swiftly dragging his brother, broken leg and all, after them. David too covered Charlie's back with a long arm, hoisting up his end of mathematician and almost lifting the smaller man off of his one good foot. In moments they had Charlie inside and lying on the sofa, white and panting. Despite his protestations, walking more than a yard or so was clearly beyond the man.

Don didn't know who to yell at first: his father—or Taylor, who'd let the older man out and into the line of fire.

Alan Eppes intercepted him. "Don't shout, Donnie. I was out the door before he could do anything. He's a nice boy. It wasn't his fault. I forgot what you told me."

"He shouldn't have!"

"It's all over," David said, trying to smooth things over. "No shots fired. No sniper. Where's Garibaldi?"

"Working the neighborhood," Taylor reported. "Shall I call him in?"

"Do that." Don wasn't ready to finish being scared. "You went over the house?"

"Twice. No bombs, nothing to report."

"I didn't find anything out of place either, Donnie," his father put in. "Your brother is safe here. Settle down."

"You're over-reacting, Don," Charlie put in. "Sniping isn't part of this guy's profile."

"Oh, so now you're an expert on profiling, too?" Didn't anyone see how dangerous this was? "And for your information, Megan is reworking her profile. Her professional profile." That sounded snide. Why did Charlie bring out the worst in him? Hadn't Don outgrown sibling rivalry? Why did that feeling of not good enough rear its ugly head every time he was around his genius brother? Don worked to tamp down his anger, to retreat into the professional agent that he was.

Charlie blinked. "Oh. Oh, that will change some of the parameters in my equation. I'll have to get the details from her. Is she back to work? Speaking of which, did you get my work out of my office? The equation I was working on for the case?" He struggled to sit up, struggled and failed.

Don gave him a hand, guiltily wishing he could somehow persuade his brother to go upstairs to bed. He looked so white! Don had never seen him like this, not even when his kid brother had had the flu a decade or two ago. He propped him up with pillows, his father pulling out a blanket to drape over Charlie.

David looked puzzled. "Colby left it in your room, back in the hospital. I didn't see it there when we picked you up, so I thought that you'd packed it away somewhere."

Now it was Charlie's turn to look blank. "I never saw it. And the nurses wouldn't let me have any paper to write on," he complained, his gaze turning accusing when he saw his brother unsuccessfully hiding a grin. "You told them not to."

"You had one arm tied up with an IV and the other protecting a chest tube," Don protested. "You keep doing numbers in your head. How was I to know that this one equation was longer than your hair?"

Snort. "Get my things out of the car," Charlie ordered. "It must be in there. Bring it out to the garage. I'll start on it there—"

"Not a chance, young man," Alan admonished him. "You're not going anywhere. I'll bring you paper if you feel you must work, but you're off your feet. That's what the doctor said, and that's what you're going to do."

Charlie exchanged an exasperated look with his brother. "Ever get the feeling that you've never grown up?"

"No. But I frequently get the feeling that you've never grown up."

"Second that," Alan said.

Charlie rolled his eyes.

David re-entered, carrying in the detritus from Charlie's hospital stay, including a large bouquet of carnations that he set onto the coffee table. The bag of plastics went onto the floor and from there, Don suspected, they would head into the trash. "Nice. Who are they from?"

Charlie shrugged. "I don't know. I thought somebody in your office sent them, for the Bureau. Megan, maybe?"

"She's on medical leave herself," Don reminded him, remembering uncomfortably that he himself had dragged the woman out to track down their suspect. "Not Megan."

Charlie shrugged again. "Maybe the Math Department. A student who's flunking, trying to earn brownie points."

"Let's take the easy way to find out. And the card says…?" David plucked the envelope from between the carnations, handing it over. "Didn't you even look?"

"Obviously not." Charlie accepted it, opened the small white envelope. It took only seconds to read it, seconds for his face to stiffen.

"Charlie?"

"I think it's for you," Charlie said uncomfortably, handing over the card to Don.

Alarmed, Don took the card by the edges, careful not to get any more fingerprints on the paper. On the white stiffened paper was:

EMIT TXEN

Even Don could decipher that one at a glance:

NEXT TIME

They ran the lead down: the flowers were a dead end. The florist had the receipt for the delivery but the purchaser had paid cash, leaving no trace. Even the receipt had been made out by the clerk, so no handwriting clues remained, simply a piece of paper directing the bouquet to be delivered to Professor Charles Eppes at the hospital. The clerk too had made out the card at the person's direction. The clerk thought that the purchaser had been a woman, but after two days and several large orders in between there were doubts.

But it didn't stop there. A number of the small white cards showed up, all bearing the same legend of EMIT TXEN. They arrived at FBI headquarters, delivered by an eleven year old girl earning ten dollars, they appeared at the main desk of Math Department at CalSci, and one was dropped off by a polite robber dressed in black as he and two compatriots emptied the trays of the clerk at a pawn shop not far from the bank that they had robbed several days ago. The pawn shop owner had been less than pleased, and had shared his feelings with the FBI in detail.

"No code this time," Don said grimly. "Nothing to decipher. What's going on? Megan?"

Arm still in a sling, Megan was back but on light duty. She almost shrugged, and thought better of it. "Good question, Don. Wish I had a good answer."

"Maybe she doesn't want to play, now that Charlie's not here in the office?" David guessed.

"It's a possibility," Megan agreed. "It would fit. She's been aiming her codes at Charlie, whether or not we acknowledged that she was. She must know that he was injured and can't work. Maybe this last job of hers was just to keep her people in line, give them some income while she waits to resume her game. How is Charlie, by the way?"

"Stubborn," Don said with a grimace. "He's got my father fretting that he's not resting. Dad's making chicken soup and all of Mom's old recipes. Charlie, on the other hand, keeps working on the equation that he says will solve this case. He's annoyed because we won't let him go out to the garage to scribble on his boards. And, by the way," Don turned to David, "how close are we to finishing his office as a crime scene? Charlie wants to see how much he can salvage from his work and the students' papers that he needs to grade."

David grinned. "You don't want to know how many students have 'dropped by' to find out how 'Professor Eppes is doing, and if he lost my paper'. I leave it to you to determine which is their priority."

"Wouldn't go back to those days for all the money in the world," Colby commented.

"Not into math, Colby?"

"Liked it and almost flunked it, freshman year, and that cured me of liking it. Moved into something easier. Never had a professor like Charlie, though. Might have made the difference."

"Don't be too sure," Megan teased. "Don, where do we go from here?"

"Nothing exciting, just good, solid detective work," Don had to say. "We follow the crimes, we run down the leads. And we hope for something to break."

What broke was Charlie's equation.

"I could have come over to the office," Charlie grumbled.

"No, you couldn't," Alan Eppes admonished his youngest. "You're supposed to be resting. This is resting? Put that leg up onto those cushions, like the doctor said to do."

"He didn't say to put it up onto cushions."

"He said to elevate it. What do you think that means, genius son of mine? Why do you think that it hurts you so much? You're not following doctor's orders."

"It doesn't hurt," Charlie told him.

"That's because you concentrate so hard on your numbers. You rest like you're supposed to, it'll hurt like it's supposed to." Alan settled himself onto the sofa next to Megan, perversely pleased at getting the last word.

"You see what I'm up against?" Charlie said, failing to hide the affection.

"The equation, Charlie," Don reminded him. "You said that you have the answer."

"Right." Charlie held up a small white board that had been dragged—and cleaned by the senior Eppes—from the garage. "As I've been saying all along, multi-variate analysis. We get enough variables on the crimes, they will fall into a pattern. We can't help it; it's human nature. We may think that we act irrationally, or can direct ourselves to behave in a random manner, but eventually we disclose a pattern."

"And you have that pattern," Don said, trying to hurry his brother along.

"I have that pattern," Charlie confirmed. "I can fine-tune it as more crimes are committed, but—"

"Next crime will be?" Don cut him off. Charlie could be awfully long-winded. This was not one of his classes.

"They go after unique places that can be dealt with swiftly," Charlie said. "There also needs to be the potential for large monetary rewards. Look at the previous sites: the jewelry store, where they grabbed what they could in less than five minutes and then left. One security guard, that they immobilized first. Few customers to maneuver around. Same thing with the bank; they didn't bother with the safe, that would have taken too long. They simply gathered up all the security people and customers, stuck them in a corner, and took what they could get from the front counters and were gone in minutes."

"But the convenience store, the bank; those aren't unique types of places," Colby protested.

"They are unique within the pattern," Charlie expounded. "After having robbed a convenience store, they've never done it again. Most criminals, when they rob over and over again, tend to do what they know. One convenience store robbed, the second will be just as easy because the suspects know what to expect. They acquire a certain comfort level with convenience stores. Ditto for banks, for jewelry stores, and others.

"Not this gang. They've never attacked the same type of business twice. And that will significantly narrow down their potential targets. We can now rule out all banks, convenience stores, jewelry stores, pawn shops, and," Charlie grinned at Megan, "aquariums."

"Very amusing, Charlie. Can we also rule out mathematics professors' offices?"

"Ouch." Charlie winced dramatically. "Next we eliminate all businesses that don't have ready cash lying out in the open, or the equivalent. They're looking for something readily convertible and not easily traced."

"So what are we left with?"

"There are still a number of possibilities," Charlie admitted, "but I'm hoping that this will improve the odds of getting there before the suspects do. What kind of places does that leave?"

"Movie theaters have the money, but too many customers around to easily control," Don mused. "Department stores? Same problem. They look for stores with well-heeled clients, a few at a time."

"How about an art gallery?" David asked, then shot his own idea down. "No. Not a lot of cash, and the art would be too traceable."

"This is like playing Twenty Questions," Colby complained. "What business has a lot of cash on hand but not a lot of customers at one time?"

Silence. Then:

"Check cashing store." Don was certain.

"That's it," Megan said, excited. "A check cashing store. Not a bank, but with plenty of small bills. Only a few customers at a time, except on a payday. And, since tomorrow is Wednesday, that would be an ideal target."

"Which one?" Colby asked. "There aren't many, but there's over a dozen in L.A., if not more."

"I think I can help there," Charlie put in. "We look at where the other robberies took place—" he struggled to unfold the map and still remain lying on the sofa. Don took it from him, holding the map up in the air so that the others could see—"and if we eliminate the aquarium as an outlier, the majority of the crimes took place in this part of town." He pointed.

"That's do-able," David said. "Off the top of my head, I think there's only one or two check cashing places in that area. We stake them both out, and we'll have our suspects."

"We'll ask LAPD for back up on this one," Don decided. "They have more manpower, and just as much desire to nail these guys as we do." He folded up the map, placing it carefully on the table where his brother couldn't get at it. "Nice work, Charlie. Now take a nap. And put your leg up."

"It's like having two fathers," Charlie grumbled, but did as he was told.