The captain peered at the computer screen. "What has that to do with my blood?"

"Human blood cells die almost immediately after they're removed from the body. Kyn's remain alive and active for three weeks. Now watch this." She ran the simulation of introducing human red blood cells into Richard's blood sample. "See how the pathogenic cells try to absorb these red blood cells, and then spit them out? It's almost the same type of toxic reaction that happens in the human liver when someone ingests wine with Tylenol. Richard can't digest whole human blood anymore."

"We know this, lady," Korvel said gently.

"Wait, there's more." She changed the simulation parameters. "I'm going to feed a little rodent blood into your sample. Watch what happens."

The same violent reaction occurred as Korvel's pathogen rejected the animal blood cells.

"I cannot feed on rats any more than I can eat shit," the captain said. "I also know this."

"But wait; there's more." Alex mentally crossed her fingers as she mixed equal portions of rat and human blood cells, and fed them first to Korvel's blood sample, and then to Richard's. A few of the cells in each sample were rejected, but the majority were absorbed. "I knew it, I knew it, I knew it. This is a fifty-fifty mix; half human blood, half rat. See? It's not discriminating as much this time."

He shrugged. "All Kyn can tolerate small amounts of animal blood."

"Yes, but this test proves that you could handle more if you drank it mixed in with human blood," she told him, running the simulation a second time. "The same way you can drink wine as long as it's mixed with human blood. Korvel, the pathogen needs blood. It lives on it. It's willing to tolerate—even absorb—foreign cells and substances as long as it gets its fix. If it doesn't, it's forced to adapt. Ergo, extra set of chromosomes and unpleasant physical mutation."

Korvel seemed dazed now. "I do not understand."

"I thought it was about physical changes. I'm an idiot. This all starts at the cellular level." She tried to think of how to put it in layman's terms. "Richard was forced to live on animal blood for years. To survive, the pathogen created a new set of DNA to process the foreign cells and attract the new blood supply. It changed Richard so that he would attract it. Like any evolving organism, it's simply been adapting itself according to its environment. If it adapts once, it'll definitely adapt again."

Korvel looked stunned. "You mean, this can be reversed?"

Alex remembered Elizabeth's threat. She'd have to cure Richard on the condition that he have John returned to the States first. Then Elizabeth couldn't do anything to him.

"We deny the new DNA what it wants, absolutely." Alex realized that a cure was also her ticket out of Dundellan, and felt like kissing the computer, the captain, and every rat in the castle. "It shouldn't take that long, either—Richard still has Kyn DNA lying dormant in his cells."

"Do I indeed."

Alex stopped feeling so great and stooped to pick up the plump tabby that had strolled in with Richard. "Hey, kitty," she said, stroking the affectionate feline. "Look what you dragged in here."

"Korvel, leave us."

"Yes, my lord." The captain walked to the door, turned back, gave Alex what she could classify only as a dire warning look, and left.

"My wife tells me that you called on her in her apartments," Richard said as he went to the lab door and locked it. "I do not recall giving you permission to do so."

"I don't recall asking permission." Alex shut down the simulation. She could tell Richard that his wife had threatened to kill John if Alex made any progress, but she doubted he would believe her. Elizabeth was his wife, the home team; Alex was the unwilling, uncooperative captive. "What can I do for you?"

"According to my captain, I killed the last of the humans we keep as blood suppliers. I cannot recall doing so, but I have lost most of the last two days." He removed his mask, revealing his distorted face and the thick layer of hair and long, bunched whiskers that had grown in.

With the hair in place, Alex finally understood what Richard had been feeding on. She looked down at the tabby, and ran her thumb through the fur around its neck, feeling a number of puncture wounds. "It's the cats. You're feeding on the cats."

Alex recalled all of the cats running around the castle. There were dozens, and half of the females were pregnant. He probably encouraged them to breed to provide him with a steady supply. And she was going to puke if she kept thinking about it.

"When the Brethren held me prisoner in Rome," Richard said, "they refused to let me feed. I endured the deprivation as long as possible, but in time it became apparent that I had to feed on something or wither away. My choices were limited to the rats that infested the catacombs, or the stray cats I assumed had wandered in from the city streets to feed on them."

"I'd have picked the cats," she admitted.

"Their bodies contained a greater quantity of blood, so I had to feed less often." He bared his pointed, feline teeth in a grotesque smile. "It wasn't until after some years of feeding on them that I discovered the Brethren had deliberately put both types of animals into the Kyn cell block."

"Jesus. Why?"

"They wished to see how feeding on animal blood would affect us." His pupils expanded to black diamonds as he limped toward her. "I expect there was some hope of soul saving or reformation involved initially. Then it seemed to become some form of entertainment for them."

"And hell for you." Despite everything she felt about the high lord, Alex experienced a small twinge of sympathy. "Nothing but cat blood ever since, right?"

"Not entirely," Richard told her, "I have never told anyone this, but I have managed to control my condition by also drinking a little human blood each day."

That supported her theory, and may have explained why Richard's Kyn DNA had remained dormant instead of being replaced by the feline-adapted DNA. "How little?"

"A teaspoon in every feeding, or a single swallow from a human. Any more than that makes me violently ill."

"Who do you get the blood from? Éliane," Alex guessed, remembering the tresora's penchant for high-necked blouses.

"Providing me with sex and blood are part of her duties." He made it sound like secretarial work.

That clinched it. "You know, you're a total jerk with women, but we'll save that chat for another time. I have an idea, if you want to hear it."

He leaned against her dissection table. "Tell me."

Alex explained why she believed the blood of stray cats Richard was forced to live on had caused the Kyn pathogen to alter his DNA, the reason behind his physical mutations. "I think I can reverse it, too. You'll have to stop feeding on feline blood."

"Do you propose to starve me, as they did?"

"No." Alex checked the refrigeration unit, but saw her human blood supply bin was empty. She couldn't remember using the last unit, but she had been wrapped up in her research. "I want to inject you with a serum. It'll be human blood mixed with a small amount of feline blood. If that works, I'll add some Kyn tranquilizer to the next batch."

"Why must you tranquilize me?"

"I'm pretty sure this is going to make you feel sick, so the tranquilizer will slow down your body processes and help keep your reaction to a minimum. The presence of the feline blood should force the pathogen to digest the human blood cells. We'll have to take it slow, but by decreasing the amount of feline blood with each dose, I think we'll wake up your Kyn DNA and put the changeling process in remission."

He looked at her for a long, silent moment. "By doing this, you will save me."

She didn't want his gratitude, or the credit for what she was about to do. "You saved yourself, Richard. If you hadn't ingested human blood daily, you would never have held on to your humanity, such as it is, for as long as you have." She hit the intercom. "Korvel, I need a unit of human blood, please."

One of Richard's servants delivered the bag of blood and, after giving the high lord a frightened look, hurried out of the lab.

"How many humans did you slaughter this time?" Alex asked as she prepared the serum.

"I cannot say." He bared his arm for her and watched as she injected him. "What does it matter?"

"Humans are our friends. We like humans. And if we kill all the humans, we don't have any dinner." She withdrew the syringe and sighed. "I hate being a vampire. It's really freaking out my brother. Have I mentioned that?"

Richard got up quickly from the stool and turned his back on her. "I can feel it moving in my veins."

"It might make you puke." She looked around for an empty container. "Just relax and let it happen."

"Let it happen." His voice dropped to a low growl. "I am done with letting it happen. It should not have happened. Not to me. I am king."

The anger startled Alex. "Richard? Look at me."

He looked. His pupils had shrunk down to slivers, and his fangs shot out of his mouth, three times longer than Alex had ever seen them.

"Right, this is not working." She grabbed the bag of blood, but it was marked as human, type A. She took a sip from it and immediately spit it out. "Goddamn it, this isn't human blood. What the hell is going on?"

"You think to poison me." Richard whipped out his arm, sending a row of beakers and a microscope crashing to the floor. "I am king. I will never die."

"Then let's go for calming down the king," Alex said softly, not moving. "Someone gave me the wrong bag, Richard. That's what's making you nuts. Hang on, and I'll—"

"Bitch." He picked up the edge of a table and turned it over. Her computer exploded in a fountain of sparks, and the cracked console of the analyzer began spitting out sample strips. The high lord tore out of his cloak and dropped onto all fours, where his twisted body assumed a new, powerful configuration.