My sister was electric.

"You two related?"

I turned to see a new boy-one who hadn't yet fallen under Kissy's thrall-looking thoughtfully at me.

"You two," he said again, jerking his head toward Kissy. "Are you related?" He had an accent, and not a Southern one, either. I tried to place it, but couldn't, and I realized that thinking about his accent probably wasn't good manners, when I could be answering his question instead.

"Sisters," I told him.

The boy nodded. He was older than me, maybe even older than Kissy, like he was already in college or working full-time at his daddy's garage. Taking a closer look, I thought that maybe he'd been out boozing the night before, because he looked real tired, and he was wearing a baseball cap pulled down over the top third of his face. His eyes-what I could see of them, anyway-were shadowed and bloodshot.

"Sisters," he said thoughtfully. "At the McDonald's at six twenty-seven."

I wasn't sure how one was supposed to respond to such a blatant statement of fact, so I went back to thinking about his accent and how his words sounded like they were coming from the back of his throat instead of the front.

That was when I saw the knife.

He held it loosely in his left hand. I was fairly certain this was a recent development, on account of the fact that I wasn't that oblivious, and the knife wasn't exactly what you would call subtle-the blade was nearly as long as my forearm and slightly curved. Its edge gleamed in the fluorescent fast-food lighting.

The boy flexed his wrist.

"I have to hurt you," he said.

I tried to take a step back, but couldn't seem to get my legs to move. "I'd really rather you didn't."

"I have to hurt you," he said again.

He stroked the thumb of his right hand over the blade in his left, allowing the metal to slice lightly into his flesh. As blood welled up on his skin, he tilted his head to the side and took a step straight toward me.

Not good. Not good. So not good.

A dam burst somewhere inside of me, and miracle of miracles, I was finally able to move. The first thing I did was start shrieking like a banshee in a yodeling contest. The second thing I did was toss the remainder of my McDonald's orange juice right in his face.

The third thing I did was run.

"Jess!" I heard Kissy yell my name, and then there was a flash of gray and yellow and plastic-sunglasses red, and the next thing I knew, my sister tackled the guy with the knife. His baseball cap went flying, and for the first time, I saw his eyes, really saw them: black-blue and glowing, like lake water at midnight, like onyx.

Like Kissy's unnaturally green eyes, only darker.

"I have to hurt you. I have to hurt you both."

Now that I could see the boy's eyes, his words took on new meaning, but he didn't exactly sound torn up about whatever compulsions he was feeling. He sounded meditative. He sounded inhuman. He sounded hungry.

Kissy got him pinned down, her hands holding his to the ground, her knees digging into his thighs. Her hair fell into his face, and like a wild thing, she growled.

She was so small and he was so big that I didn't know how she was holding him there. He fought her grip and angled the knife upward, closer and closer to her abdomen.

"I have to hurt you. I have to kill her. I have to stop this before it starts."

With each word, the boy's accent grew thicker, and the dark-light shining from his eyes spread outward from his irises until the whites of his eyes were pitch-black, reptilian and fathomless, like someone had drilled two holes straight through his head.

Kissy slammed the knife sideways, slashing her own hand in the process. Her sunglasses fell off her face, and the color in her eyes began to bleed outward the same way my assailant's had, shining brighter and brighter until I had to look away.

"I can't let you hurt her." The voice didn't sound like my sister. It didn't sound like her at all. "I have to stop you."

There was a flash of light and a sound like the snapping of twigs, the popping of knuckles. And then there was silence. I glanced at the boy behind the counter, who was now cowering against the far wall, and then turned slowly back toward my sister.

Toward the stranger who wanted me dead.

Kissy was standing. Below her, my attacker's body lay still, his head twisted at an unnatural angle to his body.

She snapped his neck.

This just did not compute. Kissy couldn't even swat flies. She couldn't play chess, because knights looked like horses and she couldn't bare the idea of sacrificing even a one.

She snapped his neck.

Her right hand was bleeding. Her hair was disheveled. She bent over, picked up her sunglasses, and put them back on. She brought her hand to her lips and licked the blood from the wound, then glanced at the boy behind the counter.

"Forget this ever happened," she told him. "You hear?"

He nodded dumbly, and Kissy turned back to me. "C'mon," she said, sounding just the way she always had, since we were little. "We have to go to San Antonio."

After the hullabaloo in the McDonald's, the truck starting up again seemed like such a tiny thing, I didn't even remember to be grateful. I was too busy trying not to chuck my biscuits all over the dashboard. My hands shook as Kissy pulled back onto the highway and put the pedal to the floor.

"Hey, Kissy?" I said finally.

"Yeah-huh?" my sister replied.

I wasn't sure how to phrase this next part diplomatically, so I just spat it right out there. "You killed that guy."

"Seems like," Kissy agreed, amiable to the core.

"Doesn't that strike you as a little, I don't know"-I searched for the right word. Terrifying? Life-altering? Insane?-"weird?"

"It is what it is, Jess." Kissy had never been one to dwell on the downside of things. "One second I was there, talking to the boy behind the counter, and the next, you were screaming, and that thing had a knife, and I just-I had to."

As she spoke, the images flashed in front of my eyes again: my attacker's dark, reptilian eyes, Kissy's shining like a pale green spotlight, the curve of the knife, the blood. . . .

I have to kill her. I have to stop this before it starts.

That was what the boy had said, and good money was on the her in question being me.

"He was going to kill me," I said, trying out the words to see how they'd sound out loud.

"I wasn't going to let him." Kissy didn't waste a second in issuing her reply, the same way she'd never hesitated to chase off playground bullies when I was in the first grade and she was in the third. "It's you and me, Jess. Always has been. Always will be."

I nodded, but my breath caught in my throat. She was my sister, and I loved her, but I couldn't shake the feeling that she was something else, too, that whatever the 'pulse was, it wasn't some genetic quirk so much as . . .

Possession. The word snaked its way through my mind, all sneakylike, and as much as I wanted to quell the thought, I couldn't quite get a handle on it, couldn't shut it down.

"His eyes were black," I said, sticking to the facts. "They were black the way yours go green."

"Yup." Kissy paused, and for the first time, the expression on her face, determined and sure, faltered. "It's kind of funny," she said, in a voice that just about broke my heart. "I always wondered if there was anyone else out there like me, and now I know."

"That thing was nothing like you." Until I said the words out loud, I wasn't sure I believed them, but they came out so fierce and so certain that it settled the matter, right then and there. Whatever Kissy was, whatever had happened to her to make her fight like that, she wasn't a monster.

She was my sister.

"Love you, Jess."

"Yeah, yeah," I said, unable to keep my eyes from her sunglasses. "I love you too."

When it came to stopping for gas, Kissy was of the Russian roulette school of thought, walking on the wild side and daring the universe to do her wrong. By the time she finally gave in and pulled into a filling station outside of Dallas, the tank had been on empty for half an hour, and I was half convinced that we were going to end up stuck on the side of the road.

There was a part of me that was hoping, just a little bit, that maybe we would. Kissy's 'pulses-even the weird ones- had always seemed so benign, but with the sound of snapping bones crackling through my memory, I couldn't help wondering why we had to go to San Antonio and what Kissy would be compelled to do once we were there.

She killed that boy. She killed him dead.

"I'm going inside to prepay," Kissy said, her voice cutting into my thoughts. "You want a Coke?"

I nodded.

"What kind?"

I couldn't help but feel like every decision I made, even the tiny ones, would bring us closer and closer to disaster. "I'll come with you," I said, postponing at least this one decision that much longer.

"You're coming with?" Kissy gave me a look. Even though I couldn't actually see her eyeballs, I translated her stare to mean, You better not be coming with me because you think I can't take care of myself.

I shrugged. It wasn't like I was actually scared that Kissy was going to go snapping necks left and right. I was just being . . . cautious.

"Maybe I should go alone," I said, knowing that I might as well be poking at an angry bear. "Your picture could be all over the news by now."

"It's not," Kissy said simply. "Nobody's going to find the body. Nobody's ever going to know."

That didn't exactly seem what I would call likely, but Kissy sounded so certain that I couldn't help wondering what she knew that I didn't, what the instinct inside of her was whispering that I couldn't hear.

"Fine," I said. "We'll both go in."

"Fine," Kissy replied, and she snapped her mouth shut and didn't say another word until the two of us were inside.

The girl behind the counter wasn't nearly so easily charmed as her counterpart at the McDonald's that morning, and she just gave Kissy and me a once-over before a bored, glassy look settled over her eyes.

"Hi, Molly," Kissy said, lifting the girl's name from the trainee tag on her shirt. "We need to prepay, thirty dollars on pump two."

Molly was not impressed with Kissy's personable nature- or her ensemble. "It's your money," she said, like the two of us were stupid for spending it on something as mundane as fuel. "Anything else?"

"A couple of thirty-two-ounce drinks," I said, since Kissy tended to take other people's boredom as a personal challenge. "And that's all."

Molly rang us up and tapped her fingernails impatiently on the counter as Kissy dug around her pockets for two twenty-dollar bills. She shoved the money across the counter, and Molly moved to take it, but aborted the action halfway through and instead caught Kissy by the wrist, her fake nails digging into my sister's skin.

Oh no. Not again.

I took an instinctive step backward, but Kissy wasn't perturbed. I looked to Molly's eyes, but they were still an everyday brown, a few shades lighter than mine. Molly tilted her head to the side, and Kissy did the same. Then Molly spoke-or at least, her lips moved and words came out, which wasn't exactly the same thing.

"They're close." The voice that spoke those words was androgynous and toneless, vibrating with so much power, it almost hurt to hear it. "Very close, and this time, there's more than one."

The bland expression on Molly's face never changed, but the words coming out of her mouth were everywhere-inside my head and out of it-until I couldn't think or hear or even remember anything else.

"You need to trust us, Jessica Carlton. Trust your sister." Even though Molly was holding Kissy's arm, she was looking straight at me, and her words came out like an order. "It starts with you, Jess. Run."

Molly dropped Kissy's arm, and if she had any recollection of the words she'd just said, she did a real good job hiding it under a healthy amount of disdain. "What're you staring at?" she asked me.

Trust your sister. The words echoed in my head. Run.

"We have to go," Kissy said. "Now."

She turned and started walking toward the back exit. My heart beating viciously against the inside of my rib cage, I turned to follow, but not before glancing back over my shoulder at the pumps. A single second stretched itself out into eternity, and then the glass on the store's windows exploded inward, and our grandfather's truck burst-red and blue and orange and yellow-into flames.

One second we were in the store, and the next we were out back, and all I could think was, They're close, and this time, there's more than one. Kissy's hand latched on to my shoulder, and she dragged me behind her, running faster than she should have been able to run.

"We have to go to San Antonio."

I normally didn't have much of a temper, but these were extenuating circumstances. Someone had already tried to kill me once today, Kissy had snapped a boy's neck, gas station attendants were dishing out prophecies, and now, someone had blown up our grandpa's truck.

"What's so bloody important about San Antonio?" I asked, taking solace in the British curse word, which was a lot more satisfying than anything my Oklahoma upbringing had to offer.

"I don't know," Kissy replied, her voice breaking. "I don't know, but we have to get there, we have to, and now we don't have a truck." She dropped my arm, and her entire body stiffened, her eyes rolling back in her head.

Not a seizure, I thought. Not now.

Behind us, the door to the filling station slammed open, and men and women of all shapes and sizes began pouring out. I shouldn't have been able to see their eyes from this distance, but there was no mistaking the darkness, the light.

"We're going," I said, holding my sister as tight as I could and hoping the words penetrated her trance. "We're going to San Antonio. C'mon, Kissy. You're okay. You can do this."

With great effort, she straightened, and the two of us began stumbling toward the road-toward San Antonio, because the 'pulse wouldn't let Kissy turn around.

Please, God, I thought. Please don't let this be happening. Please don't let this be how everything ends.

We made it to the road, maybe twenty yards ahead of our pursuers. A car slammed its brakes and swerved to avoid hitting us. To my surprise, the owner recovered quickly, leaned over, and threw open the passenger side door.

"Going to San Antonio?" he asked.

Kissy and I were in that car faster than you can say 'pulse. We didn't question how the man had known or why he was helping us.

His eyes, shining sea-foam green, said it all.

The man's name was Walter, and he was a perfectly nice sort, a few years older than Mom and Dad would have been if they'd lived. Unfortunately, Walter didn't seem to know any more about what we'd gotten ourselves into than Kissy did.