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 1

Catherine moved her flashlight over the apartment walls, tracing out complex patterns, only to get confused and having to start over. In her years as a forensic investigator, she'd seen a wide range of crimes and crime scenes. They needed a variety of adjectives to describe them. Tonight, however, she was having trouble deciding how to classify what was before her.

"This qualifies as weird," Catherine finally decided, sending her flashlight back on another trip around the walls, trying to decipher the puzzle before her. "Definitely weird. Can you make any sense of this, Gil?"

"Very little of it, actually," he said, looking up from collecting bugs off of their victim. "That's why I'm down here."

Catherine suppressed a smile at his enthusiasm. This was his first night back since having surgery to correct his hearing. He was ecstatic between his joy at being back to work and finding a collection of creepy things to examine. He looked like a very tall, graying boy in a nightmarish candy shop.

She stepped closer to examine the walls in more detail. Then she stepped further back to take in more of the scene. Her flashlight moved in another erratic dance across the plaster. After several minutes, she shook her head in a mixture of dizziness and defeat. "I'm calling Sara."

Grissom's head shot up. "It's her night off. She won't like that," he said nervously.

Catherine swung around to stare at her friend in disbelief.

"How long were you gone? Sara not like this?" she asked spreading her arms to indicate their scene. "She'll be pissed if we don't call her." Giving him a friendly grin, she moved to kneel next to him. "Gil, you can't hide forever. You'll have to work with her eventually. That," she pointed to the walls, "requires Sara. If you can't work with her, then take yourself of this case."

"And you'll do the bugs?" Grissom asked, holding a squirming bug out to his partner. When she gave him a dirty look, he sighed. She was right; Sara was the best person for this case. He couldn't put this off. "Okay, we need her. But you call."

Sara approached the crime scene suppressing her yawn. The one night she had actually decided to sleep, and she got a mysterious call from Catherine. All the older woman would tell her was there had been a murder requiring her expertise.

"Hey, David," she called as the coroner's assistant directed a body into the van.

"Sara! A pleasure as always. I thought you were off tonight," he said flashing her a smile.

"So did I," she said, too tired to pay attention to his poor attempts at flirting. "Just one vic?"

"Yeah. Grissom and Catherine are upstairs. Third floor," he said. "Got to run. See you later."

"Bye," she said distractedly. Grissom was here. Catherine hadn't mentioned that. What kind of case would require all three of them? Whatever it was, it must be high profile. There was a number of police vehicles and a spattering of TV cameras.

Crossing the yellow police tape, she headed up the stairwell. Police officers were taking statements from shocked neighbors. She found Grissom collecting bugs outside of one of the apartment doors. He looked up as she approached and gave her a hesitant smile.

"Hey, Grissom. Good to see you," she said. This was the first time they had talked in weeks. She had left him several phone messages about a case, but he had always replied by e-mail. She wondered if he was still uncomfortable around her. After she had asked him out, he seemed to be trying harder to keep distance between them.

"Sara. Hi. Sorry. About calling you in on your night off," he said. Sara decided he was nervous. She tried not to smile.

"No problem. What's up?"

"Victor Wallace, 49, Caucasian, single. Apartment manager found his body after neighbors began complaining about the smell. Multiple stab wounds," he detailed as he stood up. Grissom gave her a mysterious look. "Some cases just scream 'Sara'."

"Really?" she asked, raising an amused eyebrow.

"Really," he replied dryly, grasping her elbow hesitantly to help her over the debris in the apartment entrance. Letting go of her arm, he turned his flashlight on to move its light over the walls. She mimicked his motions.

"Wow! Is that what I think it is?" Sara asked.

"Yes," Grissom replied. He moved his flashlight to the other walls. "There's more."

Sara turned around to examine all the walls of the victim's living room. "Same thing in the bedroom and bathroom. Catherine thought you'd like this," he admitted.

"Oh, yeah," she smiled.

Each of the walls held similar cryptic scenes. Starting near the top and going most of the way down equations and mathematical formulas covered the plaster. They were scrawled messily, sometimes overlapping. Some were crossed out in broad, angry strokes, as if a demented pupil were trying unsuccessfully to solve a difficult problem.

They were written in blood.

Sara stepped over to the closest wall, running her flashlight over the assorted symbols and numbers. It didn't take her long to realize it wasn't a continuous flow. Instead, it seemed as if their perp had worked a few lines of one problem, before picking up in the middle of another. Sweeping the light over the other walls, she could detect no obvious pattern to the equations.

"It doesn't look like he ever finished a problem," she called out. "These are just parts of equations; he never carried one all the way to the end."

"I don't feel so bad, then," Catherine said, coming in from the bedroom. She gave Sara a grateful smile. "I couldn't make any sense of it."

Grissom watched as the two women examined another section of wall, Sara pointing out where one problem stopped and another began. Catherine had been right to call her in. The younger CSI had already made more progress with the equations than either of them had been able to.

Leaning back on his haunches, Grissom gathered up his evidence, stowing it carefully in his case, and sweeping the room with his eyes one last time. This case looked like the work of a signature killer. Messages were rarely left in blood unless the writer was trying to make a drastic point. Determining what that message meant would be key in catching their killer.

And Sara was better with math than anyone else in the lab. He should have called her in immediately. That he didn't bothered him. He'd avoided a getting involved with Sara partially out of fear it would interfere with their professional relationship.

That was happening anyway, and what did he have to show for it?

"You two have a handle on this? I've got to get these back to the lab," Grissom said, carefully packing the last of his multi-legged evidence.

Catherine gave him a dirty look. "It's going to take two of us a long time to process all of this," she said coldly, placing special emphasis on 'two'.

Procedure required that they start by taking bracketed photographs of each word in any writing sample, complete with a measured scale, so the graphologist, Dr. Rambar, could analyze it. Once the photographs were taken, they would need a sample from each word to verify all the blood came from the same source. Then they could move on to examining the smears to see if any trace evidence was present.

They had a scene with 12 walls covered in equations, where nearly every character would count as an individual word. It would take scores of photographs and swabs for each wall.

Grissom smiled guiltily. "Sorry, these guys can't wait. I'll send the boys over when they get back from their cases."

"Tell them to bring extra film and swabs!" Sara called out as he quickly left the room. She chuckled lightly, shrugging her shoulders when Catherine turned to glare at her.

"Glad you find this funny," the blonde complained. "This is going to take hours!"

"Thanks for calling me in on this, Cath. Glad to see someone wants to work with me," she joked.

"Gil didn't want to bother you in on your night off," Catherine replied, not wanting to confirm Sara's suspicions. Walking over to the younger woman, she handed her the photography equipment. "I've already gotten locator shots on all the walls. You can figure out what counts as individual shots. If in doubt, take multiple pics," she said. "Let's start in the bathroom. Least amount of writing in there. I'll swab as you finish each section of wall."

"Right," Sara said, not bothering to keep the sarcasm out of her voice. She went into the bathroom while Catherine gathered supplies from her kit. She gave the walls a quick glance, determining the best place to start. After a minute, she came back into the living room to examine the writing in there again.

The older woman smiled. Sara was getting better with blood analysis. It hadn't taken her long to notice.

"Is all the writing like this?" the brunette asked. She grinned when Catherine gave her an approving nod. "How did he do this? Human blood starts to congeal within 10 minutes. There's no way he could have written all this in that amount of time. But it's all consistent. There's no change in viscosity. It couldn't have coagulated."

"Good catch. We'll have Tox check the samples. There are a number of chemicals that can be added to blood to stop it from congealing. It's also possible the victim had a clotting disorder," Catherine said as Sara moved into the bathroom to start taking photographs. "So, what's up?" she asked after a few minutes.

Sara remained silent as she moved the measured scale to another section of the wall and took another series of photographs. "I broke the rules. I asked a direct question. He hasn't figured out how to answer it, yet," she replied, giving a rueful smile to her colleague. "Although, after a month, I guess that's an answer in itself."

"Must have been some question," Catherine quipped.

"No, it wasn't. That's the sad part," Sara said with a lop-sided grin.

Catherine gave her a friendly smile. She wanted to reassure her, but knew Grissom had to come clean on his own. "There's been some other things going on in his life, Sara," she said.

"What kind of things?" she asked, moving to reload the camera.

"The kind I'm not going to talk about," the blonde said, labeling another sample. "Be patient."

Sara laughed. "Cath, I waited three years before confronting him. I think I have 'patient' covered. For now. I'm not going to wait forever," she said, giving Catherine a pointed look. "Pass it on."

When the other woman put on a shocked expression, Sara laughed again. "Don't play innocent, Cath. It doesn't suit you."

Catherine shook her head as the two women returned to their work. At least Sara didn't seem too upset about this. She had to give the brunette credit: she was patient. And she would be having a talk with Grissom later. He wasn't going to be making a habit of leaving a crime scene just because Sara was working it.

By the time Warrick arrived, they had finished the bathroom and moved to the bedroom. Catherine directed him to start dusting the bathroom. Two hours later, Nick was sent to examine the trash dumpster outside the apartment building. A police officer had discovered something that looked like blood drops around it.

"I don't think I want to spend Thanksgiving around here," the Texan said when he eventually re-entered the apartment. He held up a large evidence bag containing a bloody turkey baster.

"Yuck," Sara said. "When does the trash run?"

"Tuesday and Friday. So if this matches our victim, then we have a probable time frame," he said.

"If it matches our vic?" Sara joked. "I wouldn't want to live in this neighborhood if it doesn't!" She emptied the last roll of film from the camera and placed it with the others before moving to help Catherine finish the blood swabs.

It would be well after shift ended before they took their evidence to the lab and headed home.

"What's up, Doc?" Catherine chirped as she entered the morgue the next shift.

"That's something I never hear," Robbins said dryly. "Would you like to know how your Victor Wallace died?"

"From your tone of voice, I'm going to guess it wasn't from stab wounds," she said.

"Internal bleeding. The stabbing was done postmortem," he said, sticking a gloved finger into a bloody hole. "From the wound track, I'd say the turkey baster was used to suck out the blood as it pooled in the chest cavity after death. It's hard to be exact, but it looks like your killer managed to collect about six pints."

"Wow. He would have had to waited, what, a couple hours for that much blood to collect. Any idea what caused the internal bleeding?" Catherine asked.

"Blunt force trauma to the abdomen. And he bled out quickly. We found large quantities of warfarin in his blood."

"An anti-coagulant. Explains why the blood never congealed when he was doing his homework."

"We won't know how he ingested the warfarin until we run some more tests. You didn't find any medicine bottles, so it doesn't look like it was prescribed. We'll find out more once we get his medical records. He could have been given small amounts over a long period, or a single large dose. Even then, it would take at least 24 hours before it took effect," Robbins said. "This was planned in advance, Catherine."

"I know math is hell, but yowsa!"

"Greg, did you page me just to say that?" Grissom asked in a very irritated voice. Catherine had spent more than an hour chewing him out for leaving the scene the previous night. She didn't buy his reasoning that he needed to take care of the bugs. He grudgingly admitted that he might have left to avoid working with Sara. Grissom was upset to admit that he was letting his personal problems affect his work. The blonde's warning - "You're running out of time. Fix this!" - hadn't helped his mood.

"Uh, no," the lab tech swallowed nervously. He didn't like it when Grissom was in this sort of mood.

"Good, because mathematics is the basis on which all other science is built. How can you consider yourself a scientist and not appreciate math?"

Greg started to ask how entomology was based on math, but decided he really didn't want to know the answer. And Grissom would have an answer.

"We're still replicating the blood samples you guys collected last night. As you know, oh mighty one, blood contains very little DNA. We can't test it until we make lots more of those little protein strands," he said, trying to lighten the mood.

"Yes, I know that, oh soon-to-be-unemployed-one," Grissom said sharply. "Do you have a point?"

"The blood on the walls? Definitely human. But it's not your victim's," he quickly answered.

Sara sorted through the stacks of photographs, trying to find a pattern to the equations. There had to be some sort of rhyme or reason to the scrawled writings, but she was well into a double shift and hadn't found it. Closing her eyes, she leaned her head back and rolled it from side to side, trying to unlock her stiffening muscles.

A headache was forming, but the idea of going home to sleep it off was quickly dismissed. This case was too important, and despite her cavalier attitude at the scene, she was miffed that Grissom hadn't called her in right away. As a physicist, she had a broader background in mathematics than anyone else on the team.

More than ever, she wanted to demonstrate her skills. She could think of only one reason why Grissom hadn't assigned her to the case immediately. He didn't want to work with her. That wasn't surprising; he'd often avoided her, but he'd never deliberately kept her off a case where she was the logical CSI to work it.

Who knew that a simple dinner invitation would have this type of consequence? At the worst, she'd considered that the meal would go terribly, and they'd both agree to never mention it again. She hadn't thought that it could potentially damage her career.

Sara pushed that idea down as she worked on loosening her shoulders. Grissom could have refused to let Catherine call her in. He may be avoiding her, but at least he wasn't actively interfering with her job.

A waist-high chirping caught her attention, and she pulled her pager out to find a summons to the Layout Room. Since she was already there, she raised a curious eyebrow, but started clearing away her evidence.

"Hey," Warrick called out as he and Nick entered the room. "What have you got so far?"

"A headache, mainly," she quipped. "You guys know what's up?"

"We're looking at a probable serial killer," Grissom said as he entered the room, with Catherine and a nervous Greg in tow. "The blood on the wall doesn't belong to the victim."


Greg cleared his voice nervously. Grissom's rebuke earlier caused him to get to the point directly. "I needed to wait for the DNA to replicate before I had enough to test. I decided to go ahead and type it while I waited. The victim is AB. The blood from the walls is A."

"Could the killer have used his own blood?" Warrick wondered.

"Not likely," Sara injected quickly. "By my estimate, there's about four or five pints of blood on the walls."

"How did you get that figure?" Grissom asked, peering over his glasses.

"There's about 115 linear feet of wall space involved, once you take out the windows and doorways. At any given section, the area covered by writing averages about six feet from top to bottom. About one-third of the plaster in that area is covered in blood. That gives about 130 square feet covered. A gallon of paint will cover 450 square feet. The viscosity isn't the same, but it's close enough," she said, pointing out the details on a photograph.

Grissom considered the calculations, giving a non-committal nod.

"And I tested the turkey baster. There are two sets of agglutination enzymes present. Two different blood sources. Once it replicates, I'll do the DNA profiles and run them through CODIS," Greg added, giving Sara a friendly smile.

"Make sure Toxicology tests the blood from the walls for warfarin. Our vic was full of it. He died from internal bleeding after a blow to the stomach. The stab wounds were made postmortem to suck out the blood."

"Any chance the warfarin was ingested accidentally? It's used in rat poison, and that place was crawling with them," Sara asked Catherine.

"Not likely. Doc said the levels were too high. The dosage in rat poison is real low; he would've had to eat pounds of it to get that much warfarin in his system. We're waiting on his medical records to find out if it was prescribed."

"You can get a prescription for rat poison?" Nick asked in confusion.

"Coumadin," Grissom explained. "It's what makes fresh mowed hay smell like fresh mowed hay. Back in the 1930s a bunch of cows in Wisconsin started dying suddenly. Turns out the previous summer had been very hot and very wet. Once the hay had been cut and stored, a mold developed. The mold and heat caused the coumadin molecules to bond, forming dicoumadin. This new compound interferes with the clotting action in blood."

"So any type of bump or bruise would cause ole' Bessie to bleed to death," Nick said.

"Exactly. Makes it very effective as a rat poison. They tried to use it as a blood thinner in humans, but had trouble determining an effective dose. It varied too much between test subjects. A dosage that would have no effect on Sara, for example, could be lethal for me. Even now, patients are started out on very low doses. It's gradually increased until the right level is found."

"So how did the perp know how much to give?" Sara asked. "Wild guess? Massive amounts that would kill anyone?"

"Good question. Doc said the poisoning could have been one large dose, or small amounts over a length of time. A single dose still takes at least a day to take effect," Catherine added. "He'll let us know more when the tox screens come back."

"Good. What else?" Grissom asked, looking around the table.

"Toxicology is checking the warfarin. Seeing if they can narrow down the probable source. Jacqui's running the prints. We lifted a lot of them," Catherine said.

"I've already been to Trace. I found a 2-inch fiber in the blood in the bedroom. Figured it might be from a brush," Warrick said.

"That jives with what QD said," Nick added. "A brush was used to apply the blood. Writing's consistent, too. Same person, right-handed."

"Turns out this fiber is sheep's hair, though."


The others turned to stare at Grissom.

"Oriental ink art and calligraphy. The brushes are often made from sheep hair."

"I'll check the local art supply houses. See who carries them," Catherine volunteered.

"That's a start, but he could have gotten them from a hundred different web sites," Grissom pointed out. "What about Rambar?"

"I've had copies of the photos sent to him," Sara added. "He doesn't think he'll be able to tell us much. The writing's mostly print."

"What about the equations?"

"I haven't been able to find any sort of pattern, yet. It's an odd mix. Mainly trigonometric equations. I don't recognize any of these formulas, and I haven't been able to find any references to them."

"We need to know what it means. The killer didn't just paint the walls in blood for fun," he said shortly.

Sara bit her lip, looking down to avoid the embarrassed and sympathetic stares from the others. Considering he hadn't wanted her on the case to begin with, she found his attitude vexing. Grissom was right, though. Killers didn't leave writing in blood randomly; there was a reason behind this. The quicker they found the answer, the quicker they would catch their killer.

"I know. I'll head over to the university. See if I can track down a mathematician who can make sense of it," she said quietly.

"Good. I'll go with you."

"I think I can manage at least that much by myself."

Grissom looked up in confusion. He noted Sara's angry expression and tension, as well as the uncomfortable looks from the others.

"I know you can. But I need to figure out this signature," he said slowly. "It's the most important evidence we have right now. He's leaving some sort of message. We have to find out what it means. He's collected blood from his last victim, probably to leave at the next scene.

"Let's get to work on this, people. This case is our top priority. The mayor's office is screaming to get this solved."

As he headed out to return to his office, Grissom called out to Sara. "I'll be ready to leave in five minutes. Meet me in the parking lot."

"Lucky me," she muttered, earning her a sympathetic smile from the others.

For the umpteenth time that day, Sara cursed herself silently for coming up with the idea of visiting a mathematician. They had arrived at the university to find the department had gone en masse to a conference in Reno. Deciding to try their luck in the engineering department, they found few professors in their offices during the break before fall classes began.

The dean they had finally located reminded her of a troglodyte. He had eyed her snidely and promptly rejected her initial assessment of the equations, even before he looked at them. When she pulled out the photographs, he dismissed 'graffiti' as beneath him.

A few choice comments from Grissom got the dean to re-examine the images, but he made no headway on them. Not that he tried very hard. He was distracted by his own problem, working at a whiteboard with two graduate assistants, trying to locate where they had made an error in their calculations.

Worse, the two assistants had been ogling her when they took breaks from a quiet but heated conversation. Grissom, true to his socially clueless nature, had only noticed her rising anger, giving her a disapproving look.

While Grissom tried to direct the dean's attention back to their photographs, Sara turned to face the two assistants. A hushed "We should tell them" caused her to clear her throat. When they turned to stare at her, Sara crossed her arms over her chest, blocking their view. After they looked up, she stared harshly at them.

"Is there something you'd like to share with the rest of the class?" she asked pointedly.

"Professor Brandenburg…"

"Isn't going to help," the other interrupted.

"Who's Professor Brandenburg?" Grissom asked, moving to stand beside Sara.

"He's a retired computer consultant. He moved to Las Vegas last summer. He sometimes gave seminars here, filled in for other professors," assistant one said.

"And he could help us because?" Sara asked.

"His PhD and post-graduate work were in pure mathematics."

"But he's not working any more," assistant two interrupted. "He turned down that full-time position. Remember?"

"Is he any good?" Grissom asked the dean. "And is he at the Reno conference?"

"Hmm. I suppose. He helped set up some models we use. They say he's a brilliant mathematician, but you'd think someone that smart would know what would happen when someone his weight tried to go rock climbing. Second childhood. He only got out of the hospital last week. He's still in physical therapy, so he didn't go to the conference."

"Do you think he'd help us?"

"Maybe. Call first for an appointment. He doesn't like people just dropping by." The dean excused himself to find the departmental secretary, and returned a moment later with a printout. He started to hand the paper to Grissom, but presented it to Sara after giving her a look-over. "You ask. He's a flirt. He'll like you. You're his type."

"Thanks," Grissom said, heading towards the door, grabbing her by the elbow to escort her out when he realized she was angry. He gave her a puzzled look. She usually was more professional than this. He blinked when he saw the intensity of her expression.

At the doorway Sara paused, freeing her arm from Grissom, causing him to look back in confusion. Walking back to the whiteboard, she grabbed a marker from one of the graduate students and corrected the problem. Spinning back around, she marched out of the room in a huff, leaving four confused men behind her.

In the parking lot, a page spared Grissom from bearing the brunt of her temper.

"I can't believe you," she muttered, pacing angrily around the Tahoe.

"Hmm," he said distractedly, feeling his own patience strained when he read the latest missive from the mayor. "I have to get back to the lab. You handle Brandenburg."

"I can't believe you expect me to do this."

"You can flirt," he said encouragingly, misreading her ire for apprehension. Looking up, he saw her staring incredulously at him. He shrugged defensively, wondering why she was in a bad mood. "Well, I'm not his type."