Cardinality
Summary: A serial killer is stalking the citizens of Las Vegas. Started out as a case file but the G/S aspect demanded equal representation. This is the safe version for this site. The original version can be found at my web site.
Rating: R for subject matter
A/N: No real spoilers. Many thanks to Burked for teaching me how to be a serial killer, among many other things.
Disclaimer: Obviously, I don't own anything related to CSI. If I did, certain characters would be getting more screen time – together!

"I cannot help it; in spite of myself, infinity torments me." – Alfred de Musset

Chapter 3

While the others gathered their selections from the Chinese carryout, Grissom discreetly tracked Sara as she grabbed her bagged meal and a bottle of water from the refrigerator and took a seat next to him. When she opened the bag, she cocked her head in confusion as she removed a note, nearly choking when she started to laugh after reading it.

"Joke. You had to be there," was all Sara would say, smirking when the others turned to watch her.

Grissom wondered what an acquaintance could have written that would get Sara to react so happily. It had been some time since he'd seen her in such an animated mood. She used to joke around a lot when she first came to the lab. When did that change?

He watched curiously as she folded the paper back up and leaned forward to slip the note in the rear pocket of her jeans. A sharp kick to his shin drew his attention away from Sara's posterior. Looking over, he saw Catherine shaking her head at him in a pathetic manner.

"Okay, guys," he said. "The mayor and our new sheriff want answers yesterday. Greg's confirmed the two sources of blood in the baster match the writing and the victim. We know the warfarin used was standard prescription strength. Brass is looking for leads. Catherine?"

"I checked the local art supply houses. Only three of them carry brushes with 2-inch sheep hair. We're getting their sales records. I'll go through them. Unfortunately, several of the specialty Asian markets carry the brushes as well. Some of these places are Mom-and-Pop operations. They don't have the best records."

"Work with what you can get. We don't even know that the killer bought the brushes locally," Grissom said, turning to Warrick.

"I got tire prints from the alleyway, but there's a lot of traffic through there. It leads to a parking lot used by another apartment building. I checked the stairways and fire escape. No sign of blood anywhere."

"But there were blood drops by the dumpster," Grissom clarified.

"Maybe the killer threw the baster from the window," Greg suggested. "Any drops in the alleyway could have been covered up by traffic through there."

"That's possible," Sara said, after recalling the layout of the apartment. "The dumpster would have been visible from the bedroom window. There was plenty on blood spatter on the sills. Is there anyway to tell if those drops came from a brush or a baster?" she asked Catherine.

"Not really."

"After Greg runs the agglutination enzymes from the blood samples on the sills, we'll know. If it came from the baster, there's a chance it'll have traces of both blood types," Grissom said, nodding to the lab tech, before looking back to Warrick.

"Well, I've got the victim's mail and am checking his phone records. Nothing so far. The trashcans were all empty. The only prints were the victim's," he added.

"I hauled in all the contents of the dumpster. So far, I found a couple of items with blood on them, but they're all consistent with transfer when the baster was ditched. I'm checking them all, though," Nick added, pausing to grab a forkful of lo mein. "I printed the dumpster. Lots of partials and smudges. Jacqui doesn't know if she'll be able to get anything from them, but she's trying."

"Sara's mathematician found a pattern to the equations, but we have no idea what it means. Anything else?" he asked, turning to watch her.

"I brought in the vic's computer. So far, I've gone through his e-mail and business documents. Nothing's jumping out."

"So, we have a ton of evidence, and none of it's leading us anywhere," Catherine muttered. "Bugs telling you anything?"

"Not yet, but the body was dead at least one full day before we found it on Monday. We know the warfarin was ingested roughly 30 hours before the victim died."

"So the vic was poisoned sometime before early Friday morning," Sara added. "The question is how do you get a lethal dosage of warfarin in someone? It's slow-acting. If he had been forced to take it, the killer would have to hang around and make sure he didn't call for help. There weren't any signs the victim was forcibly subdued."

"Maybe he was held at gunpoint. Or maybe he didn't know he'd been poisoned," Warrick said. "How much are we talking, Cath?"

"Doc's guessing about 15 pills were used. They're fairly small. Could have been slipped into something. A drink, maybe, or food."

"Warfarin is absorbed quickly through the stomach and the intestines. Even if there's any food left in his digestive tract, there's no way to test it to see if had been laced. Warrick, get samples from everything in the victim's kitchen. See if anything's been tampered with," Grissom said.

"I'll check any food sources in the dumpster," Nick said, pausing at a chirping sound, as the team all checked their phones.

"It's mine. Sidle," she said heading towards the doorway, a slight smile forming as she listened to the conversation. "You've been working on this all night? … Did he help? … Thanks, no, I appreciate it, Max. You've been a big help … Thanks, but I don't think I can make it this morning … No, I'll be pulling a double shift on this case … Yeah, I should be able to meet you tomorrow morning … Yeah … bye."

"Max?"

"Yes," she said, giving Grissom an odd look. "He tracked down some math historians he knows. They didn't know of anything special about the equations. One woman in New Zealand recommended a guy in Tbilisi. Apparently the world expert on polar equations. Max just got off the phone with him. There's no significance to those formulas that anyone can figure out."

"Tbilisi? Former Soviet Republic of Georgia? How much is this guy billing us?" Warrick asked in shock.

"He's not charging, as long as we provide meals. Speaking of which," she said, pulling out some receipts from her pocket and handing them to Grissom, who looked surprised at the amounts. "He eats a lot."

"I'll say."

"Damn, Sar! You really know how to make an impression," Nick said, shoving her arm playfully.

"You don't know the half of it."

"How could I find out?" Greg asked wistfully. "I'd settle for a quarter of it."

"Hey! People, we still have a case here," Grissom said irritably. When the others turned to look at him expectantly, he realized he had nothing more to add. Grabbing up his meal, he got up to head back to office. "Let's get back to work. We have two victims who need us to solve their cases."

"Maybe not," Sara added cautiously, sensing she was the cause of Grissom's bad mood. She continued when he stopped to look back at her. "We're assuming the blood on the walls came from another victim. But it could have come from some other source. A mortuary, or a hospital. The killer could have had access to biohazard materials."

"Good call. Look into it," he said, heading to his office in confusion.

What was going on? Sara was planning on seeing the man again? But the idea had made her furious the day before. It didn't make any sense. Perhaps she was just being polite. He had spent an entire day and night helping them work the case, after all.

Or she was getting even with him for sending her to flirt in the first place? She had to know he wouldn't be comfortable that routine she pulled earlier. Wouldn't she? Did this all go back to his refusing to have dinner with her?

But that wasn't Sara's modus operandi, though. Grissom sat at his desk, deciding not to pursue this line of thinking. He wasn't sure where he stood with Sara. If she wasn't going to make an issue of it, he saw no reason to bring it up.

Especially considering he wasn't sure where he stood with himself.

Everything in his life was different. In the year building up to his surgery, he knew he'd withdrawn from the others. Now that his hearing appeared to be corrected, he wondered how to close that distance. He'd damaged friendships; a quirky joke now and then wouldn't repair that.

On top of that, he felt a weight had been lifted from him; the fear of going deaf had haunted him for a long time. Now that that demon had been exorcised, he found himself looking at life in a new way. Grissom wasn't sure which way he wanted to go. Did he want to return to the relative safety of his old life or did he want to experience something new? He didn't even know if it was a journey he wanted to make by himself.

He may have waited too long for that even to be an option, and that confused him. Things were better this way – for both of them.

Really.

"Anything interesting?" Catherine asked later that morning.

"Zilch," Sara said, looking up from the computer. "This guy had a pretty basic life. E-mail messages from family and friends. Basic accounting software. Nothing elaborate about any of the files. Not a lot of money, but no real debt, either."

"Any luck tracking down the blood?"

"Not much. Biohazard materials are pretty tightly controlled. I haven't found anything, but I've contacted the Health Department to see if there's been any reported thefts or shortages. They probably won't get back to me before this afternoon."

"That was a good call," she said, pulling up a chair to set beside Sara.

"Thanks. Any luck on your end?"

"So far, the most recent purchase of 2-inch sheep hair brushes was made six months ago. A bulk purchase for a class at the community college."

"Should be easy enough to track those down."

"Yeah. So, what's up?"

"Up with what?" Sara asked hesitantly, suspecting her colleague was curious about her behavior.

"You trying to make him feel bad?" she asked sharply.

"I don't know what you're talking about."

"Uh, huh."

"Cath," she sighed. "Okay, I didn't want the assignment, but I made the best of it. Turns out Max is actually a nice guy. I'm not going to pretend I didn't enjoy working with him."

"And being catty is part of the fun?"

"Joking with my friends is. I knew the guys were going to give me a hard time about it. I decided to turn it around on them before they could get started."

"Okay," the blonde said softly. "So, you really got along okay with the guy?"

"Yeah."

"What's he like?"

"Really smart. Great sense of humor. A big flirt," she added, raising an eyebrow teasingly. "Very hairy."

Catherine let out an amused snort, as she looked up to see the receptionist, Judy, carry in a large package.

"This was just delivered for you, Sara," she said, giving the CSI an odd look.

"You know your social life is in the pits when the secretary thinks it strange you're getting a package," she sighed as she took the card. A smile broke out, prompting Catherine to ask her what was going on. "It's from Max. He apologizes for not having any coffee at the house, and since we're working a double, he sent over breakfast."

"Just how much flirting did you do?" Catherine sputtered.

"Must have been plenty, 'cause there's enough here for everybody," she said, grinning widely as she took out a large bag of coffee beans and moved to the other contents. "Bagels, different types of cream cheeses, lox, fruit."

"Breakfast?" Greg asked as he wandered in, his eyes widening in surprise. "Whoa! Whose coffee?"

"Mine. Why?"

"Yours? Since when did you spend $50 a pound on coffee?"

"What?" the two women asked in unison.

"Jamaican Blue Mountain – this is prime stuff!" Greg said, eyeing the bag wistfully.

"Go ahead and make a pot," Sara said as she set out the meal, avoiding Catherine's confused stare.

Warrick headed into the Layout Room, finding Sara going over the printouts intently. After three more days of examining the evidence, they had made little progress. None of the prints lifted where in AFIS. The DNA didn't match anything in CODIS. Catherine had accounted for all the brushes sold recently. No traces of warfarin had been found in the dumpster or in food from the victim's kitchen. There'd been no reported blood missing.

Grissom's bugs had placed the time of death on Saturday, meaning the victim had been poisoned sometime on Thursday. The police had re-interviewed the witnesses, but no one remembered anything unusual happening that day. Brass hadn't had any luck tracking down the source of the warfarin, either.

The equations remained the big mystery. Thanks to the mathematician, they knew what they were, but no one on the team had been able to make any progress determining how they related to the murder.

"See anything?" Warrick asked hopefully, moving to stand beside her.

"Nope. There has to be some reason why the guy did this. Doesn't there? Why pick something like this at random? It took a lot of work to do this. The killer must have planned it in advance. Why?" she said shortly, dropping the stack of printouts down with a huff.

"Beats me. I went over this stuff last night, looking for something. Gave myself a headache."

"Welcome to the club," she sighed.

"What about Brandenburg? Has he been any help?" Warrick said, looking up as Grissom walked into the room.

"Well, yeah," Sara said, with a brief nod. "He's been cool. I've bounced all kinds of ideas off of him. None of them have panned out, but Max has helped with all of them. Good thing he's not billing us. None of us would get a raise this year."

Grissom cocked his head to the side as he walked over to join his CSIs. Sara's admiration for the mathematician had been obvious from her tone of voice. Considering the man's reputation, Grissom was surprised Sara was so taken with him.

Maybe the attraction was professional; after all mathematics and physics were closely related. In many ways, she was a student at heart, always willing to learn something new. This mathematician was retired; he'd have the time to answer her questions. If he were a lonely fellow, Brandenburg would probably appreciate having an eager, young woman focusing on his teachings.

An odd feeling came over Grissom as he remembered when Sara used to reserve that type of attention for him.

"Hey," Sara said when she noticed him.

"Hey," he replied softly, giving his head a brief shake. "Learn anything new?"

"No," she said dejectedly.

"Don't let it get to you. Signature killers have a pattern, but with just one victim, it's hard to tell what they are doing. This," he said, pointing out the equations in the photographs, "could mean any number of things. The message may be in the equations themselves, it could have to do with the branch of math, or it could be more abstract. Without more pieces, we won't know for sure," he explained.

"But more people have to die before we get those pieces," she pointed out.

"Unless we can catch him from other evidence. Have you got anything new?" he asked Warrick.

"Nick and I went over the guy's phone records. Figured the killer had to know the victim somehow. If it was a random poisoning, how would the killer know how to find the victim's home? The vic ordered carryout from the same restaurant every Saturday night up until he died. Nothing on the night he was poisoned, though."

"And I went over his appointment book. Thought he might have had a meal with a client. His last appointment on Thursday was in the late morning at his apartment. Brass talked to the couple – they're getting ready to retire. They just went in to sign some forms. No one had anything to eat," Sara added.

"Okay. Warrick, you and Nick go to that restaurant. Check to see if he came in to pick up any carryout the night he was poisoned. It's an off-chance, but right now that's the only lead we have."

Grissom stayed behind once Warrick left the Layout Room, turning his attention to the neat rows of printouts Sara had attached to the wall. Picking up one of the folders containing the mathematician's notes, he waited as she stretched slowly.

"When was the last time you slept?" he asked, watching her closely. Everyone in the lab routinely pulled doubles, but Sara took it to extremes.

"Yesterday," she stated firmly, focusing her attention on the printouts. "As much as I normally get."

"Okay," he said, giving her a wan smile. Even he noticed the tension rising in her posture. Telling her to get more rest wouldn't be a welcomed comment, even if she could use it. Maybe a diversionary tactic would work.

"Why don't you join Catherine and me for breakfast after shift? We can go over what we know so far," he offered.

"I already have plans. Thanks. Maybe another time."

"These printouts can wait," he said kindly.

Sara turned to look at him briefly before returning her attention back to the equations. "Actually, I'm meeting Max."

"Would you prefer if I went instead?"

"No," she said, darting surprised eyes over to him.

"You have a new idea you want to run by him?" Grissom asked as he turned to give her a puzzled look.

"No, uh, actually we're heading out to Lake Mead. We're having breakfast out there."

"You don't have to do that," Grissom said sharply, causing Sara to turn to stare at him intently. He held up his hands when it seemed she was getting ready to say something.

"Sara, I know this … assignment was … unpleasant. You handled it well. If you'd feel more comfortable if someone else talked to this mathematician, that's understandable. Don't feel you have to continue to … flirt … for this case. No one expects it," Grissom said.

Sara dropped her head, before turning to look at him curiously. A hint of grin formed as she walked over to the wall to examine a graph. "I like Max. He's a nice guy. Neither of us likes to cook, so we catch meals together."

"Oh. I thought you were …" he said, unsure how to continue.

"I was what?" she asked slowly.

"I didn't want you to think you had to do anything … unprofessional … for this case."

"You actually think I'd do something like that? I have never done anything to compromise this lab or a case. Never," she said hotly, turning to face him with an angry expression.

Grissom's mouth hung open in surprise at the exchange. Of course she hadn't. He never implied that she did. Did he? As he tried to figure out how to respond, she let out a long breath, and turned back to her evidence.

"Are we done here?" she asked softly.

"I think we are," Grissom said, pausing at the doorway to look back, a baffled expression on his face.

"They're just roses. They won't bite," Catherine said as she entered Grissom's office. She smothered a laugh when he gave her a dirty look and went back to the stacks of paper on his desk. Ever since a vase of old-fashioned roses had been delivered to Sara at the start of shift, he'd been squirreled away in here.

After joking off the expensive present with the guys, Sara had moved the vase to a discreet corner of the break room. Still, the fragrance from the damask variety wafted through the lab, a subtle reminder that at least one person on the team was managing to have a social life – albeit one that nobody could understand.

Catherine had to admit she was intrigued that Sara hadn't told the guy to knock off the presents; she wasn't the type to be impressed by superficial gifts. She never would have pegged the brunette as the type to be interested in an older man. Well, one who was that much older.

"I should have taken her up on her request to go meet Max in her place," she joked. "Flowers, incredible coffee, meals, trips to the lake. He knows how to show a girl a good time."

"He's a leech," Grissom muttered under his breath.

"What did you say?" Catherine asked in surprise.

Grissom looked up, then dropped his pen on his files. Rubbing a hand over his chin, he regarded his friend cautiously. He couldn't believe Sara hadn't recognized the mathematician for what he was. She wasn't likely to listen to him, but maybe she would listen to another woman.

"He's a leech. Come on, Catherine. A retired man going after a much younger woman. He's sending her expensive gifts, monopolizing her time, taking advantage of the fact we need a mathematician for this case. He's a leech. Sara should be … careful," he said, picking up his pen to resume work.

The blonde resisted the urge to laugh. While there could be some truth to his statement, she doubted Sara would fall for it. And she found the irony amusing. "Yeah, what are the odds Sara would find an older professor through work who would actually have a real interest in her."

Grissom paused in his paperwork, and looked at his friend over the top of his glasses. Shaking his head subtly, he returned to work. The man could have a real interest in Sara, he admitted to himself begrudgingly. She had her assets.

But that didn't mean she had any feelings for the mathematician. There wasn't any significance to her going to the lake with him yesterday. She probably felt sorry for him. He didn't have any family in the area. She was just being nice.

Probably.

"Look, Gil, have you considered the fact that they might actually be friends? He's translated some articles for her that haven't been printed in English yet. They went to a talk on astrophysics at the university. They caught some meals together."

"He's sending her expensive gifts," he repeated. "How much has he spent on coffee alone? He's sent about five pounds of that stuff to the lab by now."

"I notice you like it," she said, smirking as she stared at the mug on his desk. "You know this guy has a reputation as a flirt. You know, a fella can flirt all the time, but it doesn't mean he'll ever commit to anything serious," she added pointedly.

"Do you need a case to work on?" Grissom asked bluntly.

"I'm on a break. Besides, I'm supposed to meet Doc in a few minutes to go over my hit-and-run, then I'm heading over to check some things at the scene," she said. "Look, I'll give you a clue, Gil. It's nice to have a guy show an interest in you, even if it's just in fun. And it's not like anyone else is paying her any compliments."

"Sara, Warrick, let's go," Grissom said later that night, sticking his head in the doorway of the Drying Room. They were going over the effects of the victim, trying to find something that might have been overlooked the first time. "We've got another victim. Cath and Nick will met us there when they get back from their cases."

They gathered extra supplies, and then the trio drove to a warehouse on the outskirts of town. After checking in, they crossed under the yellow tape and walked into the center of the warehouse where floodlights shone on a grisly sight.

"Oh, my God," Sara whispered.

"The killer is evolving. This is more efficient. Quicker access to the blood, and he could get more of it this way," Grissom explained.

Shining his flashlight around the scene, he walked over to examine the decapitated body of a black male. He was hanging upside-down, suspended from chains wrapped around the legs and draped over a girder. Underneath the body, a large basin held the victim's head, a look of terror frozen on his face. The body swayed eerily, his fingers dragging ghostly patterns in remnants of blood in the bottom of the basin.

"He's wearing some sort of uniform," Sara pointed out, ignoring the sharp metallic smell.

"Guy's Jim Smith, 27. Night watchman," Brass said, reading his notes. "His girlfriend tried to call him earlier. When he didn't answer, she called the security company. They sent out a Mr. Tom Sanchez," he pointed to a shaken man sitting on a box, a paramedic treating a head injury, "who passed out when he found the body, and called us when he came around. Be careful if you're around the side door. Mr. Sanchez left his dinner there."

"Warrick, start processing the perimeter of the scene. Sara," he said, passing her the camera equipment with a slight smile. "The walls await you."

Swinging the bag over her shoulder, she grabbed her kit and walked towards the far wall that Brass had pointed out. Setting down her equipment, she swept her flashlight over the metal surface, her head cocked in concentration as she tried to decipher the writing.

It started high on the left side of the wall, working diagonally lower as it came across towards the center. From there to the right side, the equations ran is a swath starting about seven feet from the floor, working most of the way down the wall.

Like the first scene, the writing overlapped, and portions were scratched out, obscuring what was underneath. Unlike the first scene, this seemed vaguely familiar to Sara. She swung her light on another trek over the wall, trying to find a pattern to the equations.

A quick walk around the interior confirmed all the writing was confined to that one wall. Returning to her starting point, she pulled out her equipment and began photographing various shoeprints in the dust around the base of the wall.

Once that was done, she moved to the right side of the wall, and began the slow process of taking bracketed shots of all the writing. After about 30 minutes, Grissom walked over to join her, watching as she proficiently worked the scene.

Rubbing his hand over his chin, he wondered whether she was upset with him. The encounter in the break room the other day had left him bewildered. There had been a definite ribald nature to her comments. He didn't believe she'd done anything unprofessional, but he didn't understand why she made the comments. He certainly hadn't meant to be insulting when he talked to her in the Layout Room.

He turned his attention back to the walls, but only for a moment. This was well out of his league. In addition to complicated formulas, the killer had scrawled out diagrams. They looked like odd loops within loops, but the lines tracing the shapes had arrowheads. Some ran clockwise, while others ran counterclockwise.

"Hey," Sara called out when she saw him.

"Hey."

"I think our perp climbed on those boxes over there," she said, nodding first to a stack of crates, and then to the writing high on the wall.

"Nick's on his way. I'll send him over to check when he gets here. This is different from the last scene," he said, looking at Sara for confirmation.

"Yeah. I think this is complex analysis, but I'm not sure. I only touched on it briefly in college," she said, stopping to load another roll of film in the camera.

"Complex analysis?"

"Calculus for the complex number system."

"There's a special type of calculus for imaginary numbers?" he asked in surprise, giving her a brief smile when she turned to him.

"Yeah," she said, moving the scale to the next section. When she looked up again, she saw his confused look. "We used a little bit of it in my electronics classes. Because of the phase and angular components of alternating currents, imaginary numbers pop up."

"Of course they do," he said, raising an eyebrow in amusement. "I'll take your word for it. What do you recognize?"

"See that thing that looks like an upside-down capital-ell?" Sara said, nudging Grissom's flashlight to shine on a -shape.

"It's the Greek letter gamma. I do remember that much," he said in a mock-pout, earning him a hint of a grin.

"It's used in complex analysis to designate a contour. That's a collection of joined line segments," she explained.

"Any idea what any of this means?"

"Haven't got a damn clue. Or how it relates to the last set of equations. I'll call Max in the morning and see if he can help."

"Fine," he said oddly, turning to walk away. "I'll send Cath over to help you swab the walls when she gets here."

"Greg ran the assays on the blood from the walls. It's from our first victim," Catherine said as she entered the break room. Sara looked up from her folder, nodding slowly.

"So, we have two dead bodies and three types of blood. You guys find anything useful at the crime scene?"

"Doesn't look promising. They don't store high-value items at the warehouse, so they don't have any security cameras. Lots of truck traffic through there. Tire tracks are too mixed up to make any sense of. There are hundreds of prints. It'll take Jacqui a long time to compare them all to those we lifted from the first scene," Catherine sighed.

"And no one besides the security guard was in the area. No witnesses to interview," Sara added.

"Brass is talking to the girlfriend, trying to find out what he's eaten in the last 30 hours. The blood in the basin never congealed; I'm guessing it's a safe bet we'll find a shitload of warfarin in his system."

"Nick lifted some shoeprints off of the crates. He's trying to match them up to a brand."

"Goodie. We get to play Cinderella with all the workers," the blonde said sarcastically.

"I'm going over what we know about the victims. So far, I haven't found anything to link them, other than the fact they're both male. Different age group, different race. Wallace was an insurance salesman. Smith wasn't a client. They lived in different neighborhoods. Hung with different crowds, no pun intended," Sara said.

"What about the writing?"

"Completely different branch of mathematics, even though both are marginally related to calculus. I called Max, and he is coming over later this morning when he gets out of physical therapy," she said, flipping a page in the folder.

"Seems like you made a friend."

"Hmmm?"

"He's not getting paid, but this guy is going to a lot of trouble to help us," Catherine said lightly.

"I think he's finding retirement boring."

"And Max finds you interesting?"

"I wouldn't know, Cath," she said, her lips turning up slightly.

"Uh, huh. And who did you meet for breakfast the other day?"

"He's a friend. I wanted to thank him for helping."

"Uh, huh. And that explains the expensive coffee, breakfast for the whole lab, the flowers?"

"He's a flirt," Sara sighed.

"Sure he is. And you love the attention," she insisted, causing Sara to smile behind her folder. "I've got to take Linds to the doctor. She's got some sort of bug. I'll be back later. Page me if you need anything."

"All right," she said, turning her attention back to her notes, trying to find what linked their victims to the killer.

TBC