Author's Notes: Thank you for your reviews, you're all so awesome. If anyone here has read The Strange Case of Dr. Jekyll and Mr. Hyde and not just heard of it should enjoy a few little nods to it which will come later. Points to whoever recognizes them!

Nick found himself jogging back into the parking lot and jumped into his car as fast as he could. He took off in the direction he'd seen Greg's car go in earlier, having nothing else to go on until his phone began to ring.

"Hello," he said absently into the phone as he concentrated on the road.

"Car crash on I-15," came Ecklie's voice. "I need you to check it out."

"I'm busy right now," Nick replied.

"So is everyone else," Eckile said harshly. "All working on the Samson case, just do it."

Nick ground his teeth. He was just turning onto the interstate. "Good bye, Ecklie."

"Don't hang up on me—"

Nick hung up his phone, fully aware that he could have just gotten himself fired but not willing to think about it at the moment. He needed to get off the highway before he ran into the traffic caused by the crash, even at five o'clock in the morning.

It was too late. Cars were already backed up. "Shit," Nick cursed as he hit his wheel with his hands. He leapt out of the car and wove between the cars until he saw the crash. His heart stopped. It looked like Greg's car, slammed straight into a tree in a ditch off the road. Nick broke into a run and as he got closer, he saw cops by the passenger door.

"What the hell is this?!" Nick yelled.

One of the officers looked up at him. "Oh, you're CSI," he said, noting the vest. "Thought you were another pissed off driver. Two victims, male and—"

"Female," Nick interrupted. "Yeah, I know, I know this car, are they OK?"

"They're both unconscious," said the officer. "The girl, she's breathing fine, but the driver is going into convulsions."

Nick muttered a few other profanities before running over to the driver's side and pushing the cop out of the way.

It was him. Greg was sweating and shaking, his head bleeding. Nick looked at his window and saw it had been smashed, with traces of blood. Greg had to have hit his head on it pretty hard.

"Where are the paramedics?" he demanded.

As if in reply, an ambulance pulled up and they started jumping out. Nick backed away from his scene and put his hands over his mouth, breathing deeply. He took out his cell phone and dialed.

"Hey, Ecklie? Yeah, turns out the car crash was on my way after all. Listen, tell Grissom something bad has happened…"

Grissom looked at the virus on the monitor connected to the electron microscope and compared its DNA to the DNA it was altering. He bit his lip and went over to change the slides.

"What's the point of this?" Hodges asked, surprising Grissom and the slide slipped.

"Thank you for that, Hodges," Grissom said, closing his eyes.

"Honestly, though," Hodges said. "I've looked at that myself you know. Mia asked for my… expert opinion."

"I'm sure she did," Grissom mumbled, repositioning the slide. "And you were just too happy to give it."

"If you're trying to identify the virus, give up," Hodges said. "It's unlike anything Mia and I have ever seen before, so I doubt you would recognize it. Protein layer is completely alien, and the way it attacks the cells—"

"Actually, I was looking at its DNA," Grissom interrupted. He used the pointer on the microscope to center it on a specific point. "It's more tightly coiled then human DNA, and its amino acids dissolve when inside the cytoplasm of its host cell, which explains where the mutated human DNA gets its extra information… Check this out."

He moved to another table. "On one of these chromosome maps, you'll see the allele for a heterozygous dark-eyed individual. In the second, you'll see that same DNA after it has been altered by the virus."

Hodges frowned. "That's not right," he said. "Where's the marker?"

"Absent," said Grissom. "The heterozygous dominant individual has just become a homozygous recessive individual."

"That doesn't make sense," said Hodges.

"The virus replaces the allele," Grissom explained. "It removes the dominant dark-eyed trait and replaces it with the recessive light-eyed trait."

"We knew the virus altered DNA," Hodges said.

"But we didn't know it would have this kind of a side effect," Grissom said.

"You're right," Hodges said, catching on. "Normally when DNA is altered, the cell can no longer reproduce it properly, like with the oncogene. It promotes tumor growth; it doesn't result in an actual success."

"But this mutation is so seamless," Grissom said, "that when cells in the eyes read this new information, they copy it like they'd copied the old information all their lives." He frowned at Hodges. "When the virus is at its peak of activity, it can actually alter the appearance of the individual."

"What's that mean for Greg?" Hodges asked.

Grissom's heart beat loudly in his chest. "That he is literally becoming two different people."

"Grissom!"

He looked up at his name. "Conrad," he said, respectfully.

"Nick Stokes is investigating a car crash," said Ecklie. "Thought you might be interested in its victims."

Sofia saw him waiting anxiously in the waiting room. "Can I help you?"

"Yes," he said, rising to meet her. "I'm here to talk to Warrick Brown? My name is Brandon Carter, he wanted to speak with me about Katerina Samson."

"Oh," said Sofia. "Yes…"

" Sofia," Warrick said as he entered. "Mr. Carter, thank you for coming down. Sofia, care to join us?"

"Info on the Samson case?" Sofia looked fleetingly over her shoulder, and then nodded. "Sure," she said. "This can wait."

They escorted him to a quieter room and sat down. "Mr. Carter, I've noticed a few incongruities with your law firm."

Carter nodded. "Yes, I was afraid of that. We're not doing anything illegal, if that's what you're wondering. If we were, I wouldn't have offered to come down here."

"So what exactly are you doing?" Warrick asked.

"One thing I didn't fake is my law degree," Carter replied. "We're clandestine because some of the things we do just barely scrape the surface of being legal. Also, are clients like their confidentiality. I really am a lawyer, but my employees are scientists. Just like you."

"Just like me," Warrick said with a smile. "So tell me what your clients are like, Mr. Carter."

"Big companies and the like," said Carter. "We do the jobs no other research facility has the balls to do. Let's just leave it at that."

"What about Katerina Samson?" Sofia asked. "What was her part in all of this."

"Katy," Carter said, "was one of my scientists. A doctor in biochemical engineering."

"And you just happened to be neighbors?" Warrick said.

"If you think there's some sort of affair between us, you're wrong," Carter answered, sounding offended. "I was her boss, that's all. Hell, Samantha lives in that neighborhood too. She's my partner. All our employees live within a ten mile radius. It's an easy excuse to meet late at night without drawing the attention of the families. Katy would borrow a lawn mower from me and return it every time she wanted to run a few things by me."

"What was she working on?" Warrick asked.

"I'm afraid that's classified," Carter replied.

"More of your barely legal activities?" Sofia asked.

Carter flashed her a grin. "You could say that."

"Don't make me get a warrant, Mr. Carter," Warrick said, sounding tired. "Because I will, and I really don't care about your almost-legal research facility, or what happens to it after we find out it's a little less legal than you claim."

Carter closed his eyes. "She was working on a biological agent. Its purpose was meant to be used on assassins, soldiers, and the like. People who would need to leave their morals at the door, so to speak. The project is still in its infancy. So far it's killed every specimen it's been used on, which is not our intention."

"You want to turn folks into killers," Warrick said. "Not have them killed."

One corner of Carter's mouth began to rise up as he gave Warrick a disturbing half-smile. "We are all two different people in the same head, Mr. Brown. Everyday we walk the fine line of what we want to do versus what we should do. We'd all cross it if we thought we could get away with it. That's all this agent does. It lowers all our inhibitions, takes away our conscience and all we know is what we want, and we go after it with a vengeance. It destroys our own private mental restraints. There is no good and evil. The world is a mass of grays and black. There is no white. Just almost white."

"And where would your organization fall?" Warrick asked.

There was a knock on the door and Grissom entered, looking grim. "Warrick, Sofia," he said. "Can I talk to you?"

Carter's half-smile quickly turned into a full one. Warrick turned to Grissom, annoyed. "Grissom, I'm in the middle of—"

"I know," Grissom replied. "It's about Greg."

Warrick stood up. "What's going on?"

Grissom nodded at the door. "Sir, would you mind waiting a few minutes?"

"I got to be at work in two hours," Carter said.

"You'll get there," Grissom promised.

Something about Grissom's voice bothered Warrick. It was utterly emotionless, which wasn't completely unlike Grissom. But Warrick noticed that it wasn't just emotionless, it sounded completely dead.

"What's wrong?" he asked.

"Greg and Sara were in a car accident," Grissom said. "Although I'm not so sure it was an accident."

"You think Greg did it on purpose?" Warrick said.

"Why would he do that?" Sofia asked.

"He's been infected," Grissom explained, "with some sort of biochemical virus."

"No shit," Warrick muttered, turning around.

"Where are you going?" Grissom asked.

"Finding out what the hell kind of trick this guy's trying to pull," Warrick replied.

When he entered the room again, he slammed the door. Sofia and Grissom entered quietly after him as he pounded his fists on the table.

"Whoa!" said Carter, leaning back in surprise.

"You say you're a lawyer?" Warrick asked.

"Yes," said Carter.

"Good, that means I don't have to tell you to get one."

"What's this about?" Carter asked. "I was cooperating, I don't want any trouble for Bennett & Locke."

Grissom stepped forward. "A CSI was infected with a virus of unknown origin. It causes a specific form of dissociative identity disorder, one in which we act on our most primal desires." Grissom replied.

Carter paled. "That's impossible. That agent is still in its experimental phase, it's not safe—"

"We have reason to believe that Matthew Samson is also infected," Grissom replied.

"Katy's husband? That's…" He trailed off. He then looked at Warrick. "OK. One of my doctors noticed that there were a few vials missing. But Katy said she'd used them on our 'lab rats.' I thought it was rather odd, because she used chimpanzees—you're not going to get PETA involved in this are you?"

"If Katy stole the virus, why did she give it to her husband?" Grissom asked.

"She was always anxious to test on human subjects," said Carter. "I was willing to give her the chimpanzees, but humans, that's a legal line I'm not ready to cross."

"She used her own husband as a guinea pig…" Warrick said, sounding disgusted.

"There could be more to it," Carter said. "The virus increases the sex drive. She might have seen that as a perk. Bennett & Locke isn't responsible for this, you can't charge us for anything."

"If Matthew Samson dies," Grissom said, his voice low and slow. "Or if Greg Sanders or Sara Sidle dies as a result of your virus, you can bet damn well we can charge you, and you know it." His voice reminded Warrick of a dog uttering a low growl at the back of his throat as a warning to trespassers not to take one step out of line.

"Who are those people?" Carter demanded. "The virus didn't do anything to them."

"Greg Sanders," Grissom continued, in that same low tone, "is the infected CSI, and Sara Sidle was in the car with him as the virus made him crash it into a tree."

Carter groaned. "Jesus, Katy, what did you do?"

Grissom's phone rang. "Jim?" he said, answering the phone. He nodded and hung up. "I got to go. Matthew Samson is threatening to kill himself."

If possible, Brandon Carter went even paler.

"Catherine," Nick said as she arrived at the scene.

Catherine took in the car. "Greg and Sara are at the hospital?"

"And we're here to do our job," Nick said with a sigh.

"How are they?" Catherine asked.

"It looks worse than it is," Nick said. He pointed inside the car. "Airbags deployed, for one. Greg banged his head against the window pretty bad, but Sara looked like she braced herself. She had some cuts and contusions around her arms like she put them up to cover her head."

"They could have both been killed…" Catherine said. "The virus did this?"

"Aw, Jesus," Nick said, putting his hand over his eyes as he walked away from the car. He kicked the dirt and let out a slew of obscenities.

"Nick?" Catherine called over to him. His back was to her as he was staring down at the highway. She saw him shaking his head. Armed with a warm smile, she approached him and rubbed his shoulder. "Nicky…"

He looked up at her with tired eyes. "It's been a long night," he said. "Sara's in the hospital for the second time tonight. Greg is infected with some virus straight out of a fucking… Robert Louis Stevenson… shit… and we don't know how to fix it."

Catherine didn't know what to say. She had all the same doubts Nick did. "You said the crash wasn't so bad."

"For Sara," Nick said. "She was smart. Greg was going into convulsions by the time I got here."

This news really made Catherine's heart sink. "Oh, Greg…" she said, regretting her annoyance with him earlier. "I shouldn't have leapt to conclusions so fast."

"I don't know why we're here," Nick said, frustrated, "and not at the hospital."

"It's like you said," Catherine said, looking over the car wreck. "We have to do our job."

"What's there to say?" Nick asked. "Greg was sick, he crashed the car."

"Intentionally?" Catherine said, softly.

"Possibly."

"And why?" Catherine added.

"I don't care," said Nick. "It's a car crash, plain and simple, what does it matter?"

"It matters to the insurance companies," Catherine replied. She looked at the car again. "I'll tell you what, Nicky. This doesn't look like a two person job. Why don't you go on over to the hospital and check up on Greg and Sara. I'll finish up here, tell Grissom what went down."

"Aw, Cath," Nick said, shaking his head. "Nah, I can't leave you here, not by yourself, Grissom would have my ass on a platter."

"I'm not by myself," Catherine told him, pointing to the surrounding cop cars. "You got about a couple dozen people here. I won't get mauled. I won't disappear." She hesitated and put a hand on his arm with a sympathetic smile. "And I won't be held hostage by a convict's crazy father. Relax. Everything will be OK."

Nick took her hand off his shoulder and held it a moment as he returned her smile. "Thanks, Catherine."

"Eh, it's what I'm here for," Catherine said with a shrug. "Now shoo. I expect a full report on how Sara and Greg are doing by the time I get there."

"Yes boss," Nick said with a wink, and with that, he left.

"I would have gone to get you," Brass said as Grissom, Warrick and Sofia entered, "but I had to make sure he didn't do anything."

"He doesn't have a weapon," Sofia said. "How can he…"

"You didn't see him earlier," Grissom muttered.

"Look at his eyes…" Warrick said. "They're blue."

"That would be the virus," Grissom said. "Altering his alleles."

"It changes his eye color?" Warrick said skeptically.

"It bleaches his genes," Grissom corrected. "Blue is a recessive trait. Hodges and I figured it to be a side effect. The virus carries the extra gene in its DNA."

Grissom and Brass entered the room. Grissom addressed Matthew slowly. "Matthew? My name is Gil Grissom, we met at your house, remember?"

Matthew was shaking and drenched in sweat as he shook his head. "Dead. Dead. All of them, all of them, dead." He looked over at Grissom. "He told me everything, you know. He told me that they had to die. They were her spawn. Oh God, I didn't want to kill them. I loved my babies so much." He began to cry as he softly sang to himself. "We always hurt the ones we love. That's why she hurt me, isn't it? It wasn't my fault. It wasn't his fault. We're the same, he and I, we're the same. He tried to tell you. He tried to tell you it wasn't our fault. I loved her and I trusted her and she broke my heart. And I thought she was offering to cook dinner because she loved me."

"He's been talking like that for twenty minutes," Brass told him. "Don't even think he knows we're here anymore."

Grissom slowly approached Matthew. "Matthew? Do you hear me?"

"DON'T COME ANY CLOSER!"

The yell echoed throughout the halls. Sofia jumped. "This is creepy," she muttered to Warrick, who nodded in agreement.

Grissom, of course, froze in his tracks. "Alright," he said. "I won't move. Talk to me. How long was she drugging you?"

"Too long," said Matthew, shaking his head. "Far too long. At first, she was pleased. Very pleased. When she slept with him, she told him everything. He knew. He saw the poison. She showed him. When I woke up with her the next morning, she didn't like what she saw. She only loved the half of me she created. He was the only one who could control her. But I didn't know. He knew the difference, but I had no idea. I loved her anyways." For the first time, Matthew looked directly at Grissom. "Do you know what it's like, Mr. Grissom? To have half of you living your entire life in secrecy and then finally when you come out… You're forced into secrecy. He becomes everything. You become… nothing…"

"I'm sorry about what happened to you, Matthew," Grissom said. "I was wondering, could you tell me what happened to my friend, Greg Sanders?"

Matthew smiled and nodded. "Blonde tips," he said, knowingly. "He had been going for the girl, you know. The girl. He wanted his legacy to live on, you see. She was dead, our Katy was dead, but the girl was alive. She wasn't evil, like Katy, but she could be under the right persuasions. We found the guy instead. Blonde tips. He didn't mind. He wanted a friend."

"So you took one of Katy's syringes," Grissom said.

Matthew nodded. "The ones she brought in from work. Grabbed him at the stairs. Stuck him in the arm. He was confused and he stumbled. I took him outside. He tried to hit me, but missed. Then he threw up. After that, he grinned at me. He thanked me."

"Matthew," Grissom said. "You didn't remember any of this before. How do you know what's happened to you? What the other part of you did?"

Matthew stared off into the far corner. "He's gone now. Flew far away. Like a bird. Or an angel. My kids are angels now, did you know that? Before he left, he told me everything."

Grissom squatted down to try and look Matthew in the eye. "Matthew…" Grissom said slowly. "Will he come back?"

"No…" said Matthew, shaking his head. "He can't come back now. Not unless she poisons me again. She can't do that though, you know. She's dead."

Matthew stopped shaking. His blue eyes continued to stare into the far corner of the room, wide and empty. His lips parted and curled into a small smile. He laughed a dry, curt laugh and then stopped abruptly. He stiffly fell over onto the floor and didn't move. His eyes were still open and he was still hugging his knees, but Grissom didn't need to check his pulse to know that he was very much dead.

Grissom slowly rose to his feet as he stared at the body of Matthew Samson.

"Brass," he said, his voice quiet. "Across the hall, Warrick has Brandon Carter, head of the agency that created this virus. Would you be so kind as to go and arrest him please?"

Brass nodded and left the room. Warrick and Sofia entered.

"He's dead," Warrick said. "What's that mean for Greg?"

"Greg only got one dose," said Grissom. "Although by the sound of it, I'll bet it was a high one. Hopefully, he'll sweat it out. Fight it like any other disease."

"There's no cure?" Sofia asked. "We can ask that Carter guy, maybe they have one."

"He said the virus was still in its early stages," Warrick replied. "I doubt they've gotten around to making the cure yet."

Grissom stared at Matthew Samson's body for a long time. "They never do," he said.