A little girl with long black hair and black whiskers drawn on her face opened the door to Brendan's house and shrieked at the top of her lungs, "IVY'S SISTER'S HERE!!!" Then she grabbed Olivia's hand and pulled her inside. "Want to see my room?"

"Um," Olivia said, glancing around. "Is Brendan home?"

"His room's boring." The little girl sighed, rolling her eyes. "Come on!" she said, dragging Olivia toward the stairs.

"What's your name?" Olivia asked.

"I'm Bethany," the little girl declared. "And I'm seven, but I'm utterly mature."

Bethany pushed open a door that had a DO NOT EXPOSE TO SUNLIGHT sign on it.

"So you're a cheerleader?" Bethany asked.

Olivia nodded. "I think cheerleaders suck. Look!"

she said, kneeling down in front of a black dollhouse.

She reached into a tiny bathroom and produced a Barbie doll that had red pom-poms glued to her hands. "Do you like her? She lives in the bathtub."

Olivia laughed, taking off her jacket. "Does she know any cheers?"

Bethany nodded and made the doll hop around on the floor. "Two, four, six, eight. The bunny hop is really great!"

Olivia made the sound of a roaring crowd.

Bethany giggled. Then she said, "Will you come play with me after Ivy moves away?"

Olivia felt an ache deep in her heart. She nodded silently.

Bethany smiled gratefully, even though her eyes were on her doll, which she was making do somersaults.

"I'm going to miss Ivy," she said quietly.

"Me, too," whispered Olivia.

"Here you are," a familiar voice announced.

Olivia looked up to see Ivy standing in the doorway.

"Everyone's waiting to meet you in the kitchen," Ivy told her. "Hey, Bethany," she said, "want to do the spider?"

"Yeah!" Bethany shrieked. She ran up to Ivy, then turned around, put her hands on the ground, and flipped her legs up into the air. Ivy caught them and steered the little girl down the stairs like a wheelbarrow as Olivia followed. "Did Olivia tell you that we're going to be in Vamp?" Ivy said to the soles of Bethany's feet. "You are not!" Bethany lifted one hand off the ground and twisted around to look up at them.

"We are," Olivia confirmed. "Maybe we'll autograph a copy for you."

Bethany squealed and spun back around.

When they entered the kitchen, a middle-aged man with crazy gray hair and round glasses hurried across the room. "You must be Olivia," he said excitedly. His gaze flicked from Olivia to Ivy. For a moment, Mr. Daniels seemed completely lost in his own thoughts. Brendan came up and gave Olivia a hug.

Brendan's father leaned forward and peered into Olivia's ear. "Inconceivable!" he murmured.

"Dad?" Brendan said in an embarrassed voice, and Mr. Daniels snapped out of it.

"Oh, yes!" Brendan's father blurted. "I mean, yes, inconceivable how much you and Ivy look alike." He took off his glasses and polished them with his shirt. "Not that it's amazing for twins to look alike. Just that you're so different." He laughed uncomfortably. "But not too different.

Oh, dear," he finished, suddenly shutting himself up and putting his glasses back on.

Olivia could tell Mr. Daniels was trying desperately not to give anything vampish away, but she just nodded like she had no idea what he was fussing about.

A woman wearing a gray pin-striped blouse tucked into black slacks gave Olivia a warm smile.

"What my husband is trying to say is that it's a pleasure to meet you," she said, coming over to give Olivia a peck on the cheek. "I'm Brendan's mom."

She handed her husband some long tongs. "We're cooking on the barbecue grill outside," she explained. "But, don't worry, we're eating indoors."

A few minutes later, Mr. Daniels, now wearing an apron and clutching the barbecue tongs, stopped next to where Olivia and Ivy were sitting at the kitchen table. "So, Olivia," he said, clearly trying to sound casual, "what are your favorite foods?"

"Tofu," she answered.

"Ew!" cried Bethany from where she and Brendan were playing with toy elephants on the floor.

"Inconceivable," Mr. Daniels muttered again.

His eyes focused on her shoulder. "Hmmm," he said, unconsciously reaching down and plucking a loose strand of hair from Olivia's shirt.

Just then, Mrs. Daniels came over with some pink lemonade.While Olivia was taking the glass, she saw Mr. Daniels carefully put the hair into his shirt pocket.

I bet he's going to test my DNA, Olivia thought, slightly weirded out. But I guess one hair won't hurt.

Mr. Daniels ventured outside to cook, leaving the door open so he could still join in the conversation.

"So tell me," Mrs. Daniels said to Ivy and Olivia, "what was it like when you two first met?"

"Surreal," Olivia and Ivy both said at once.

Mrs. Daniels nodded like she understood. She exchanged glances with her husband. "You must have wanted to share all your secrets with each other right away."

Ivy shot Olivia a paranoid look, clearly worried that the Daniels were onto them. Olivia studied Brendan's parents' faces: Mrs. Daniels looked so sympathetic, and Mr. Daniels seemed so eager.

They want to talk openly, Olivia thought, just as badly as we do. She looked at Ivy hopefully, but her sister responded with a brisk shake of her head.

Bethany suddenly came over to the sisters, twirling like a top. "I can't believe you're going to be in Vamp magazine," she shrieked, "with all the most famous vampires in the world!"

Mrs. Daniels breathed in sharply, and outside, Mr. Daniels's barbecue tongs clattered to the patio. Ivy looked completely panicked and Bethany suddenly froze, mid-swoon, realizing what she'd done.

"Oops," she squeaked.

"You didn't really mean vampires," Mrs. Daniels said hurriedly, "did you, dear? That was just your little game."

"Q-quite an imagination," Mr. Daniels stammered, coming inside.

All at once, tears began pouring out of Bethany's eyes, making her whiskers run. "Am I going to be condemned?" she bawled.

Mrs. Daniels bent down to comfort her as everyone averted their eyes. Olivia felt terrible.

Bethany was clearly going to be scarred for life if Olivia didn't let her off the hook. She crept up and took the little girl's hand.

"There aren't any vampires, I swear!" Bethany sobbed, shaking her head wildly at Olivia, her face soaked with tears.

"Bethany, it's okay," Olivia responded kindly.

"I already knew."

We're staked! Ivy thought, her stomach sinking as she waited for horror to spread across the faces of Brendan's parents. Instead, Mr. and Mrs. Daniels exchanged knowing looks, and Mr. Daniels bent down before his daughter.

"My nightingale," he said, "you must never, never talk about vampires." He glanced toward Olivia. "Especially when there is anyone around that you're not absolutely sure is one of us. Do you understand?"

Bethany nodded and wiped her nose on her sleeve.

Mr. and Mrs. Daniels turned to Ivy.

Brendan's parents are going to hate me forever! she thought. "I didn't mean to break the First Law," she blurted.

"Of course you didn't," Mrs. Daniels said.

"But how could you not have? Olivia's your twin sister, after all."

Brendan came up behind Ivy and gave her shoulder a supportive squeeze.

"This is an exceptional case," Mr. Daniels agreed.

Ivy felt relief spreading over her. It was like walking out of hot sun into cool shade.

"Remember the last time a human was told, Marc?" said Mrs. Daniels.

"I thought I was like the only one ever," Olivia said nervously.

"It is very rare," Mr. Daniels admitted, "but a handful of humans have learned the Blood Secret."

"Of course, there was a time when anyone who discovered the existence of vampires was killed," Mrs. Daniels said. Ivy noticed her sister turn white. "But things are different now."

"What happened the last time?" Ivy inquired.

"His name was Karl Lazar," Mr. Daniels said, stroking his chin. "The story made quite a scandal in the black papers, because he was the son of a vampire count. And Karl didn't just break the First Law. He broke the Second Law, too."

"Falling in love with a human," Mrs. Daniels clarified. That's what must have happened with our parents, Ivy thought.

"Yuck!" little Bethany exclaimed.

"So what happened to him?" Ivy asked uneasily.

"The Lazar clan was strongly separationist," Mr. Daniels said. "It was the worst of all possible situations." Ivy thought of her father, and how he refused to meet Olivia.

"Karl ended up in exile, living with his human mate. He was completely isolated from his community and his family," Mrs. Daniels concluded, and Ivy felt like a tiny stone had dropped inside her stomach and hit the dark bottom. Is that how I'm going to end up, cast out because of my relationship with my sister? she thought.

Mrs. Daniels looked at her children tenderly. "I don't know how parents could stand to sever themselves from their own children in that way."

A few minutes later Mr. Daniels unobtrusively gestured to Ivy that he wanted her to come outside to the barbecue. Ivy hurried over. Mr. Daniels was turning steaks. He pointed with his tongs at an unappetizing brown disk in one corner. "Do you have any idea how to cook one of these veggie burgers?" he asked in a low voice. Ivy shrugged apologetically.

"The things humans find appetizing," Mr. Daniels murmured. "Inconceivable!" The smoke rising around his head made his wild mane of gray hair appear even larger.

"Olivia and I read your research online," Ivy said. "Do you really think it's impossible for a vamp and a human to have babies?"

Mr. Daniels's glasses flickered with the reflection of the barbecue's flames. "That is exactly why I find you and Olivia so extraordinary," he said.

"Science is the study of empirical evidence. It is about what we can prove physically. And the existence of twin sisters, one vampire and one human, is nothing if not physical proof. I'm not certain what the two of you prove exactly. But we shall find out!"

He grabbed a fork from beside the barbecue and speared the veggie burger. "Imagine this is human DNA, the fundamental building block of human life," he said. In his other hand, he picked up a huge steak with his tongs. "While this is vampire DNA, the essence of our existence. My research says they are incompatible." He flung them both back on the barbecue, and the flames flared wildly. "But perhaps there is something we are missing."

He sighed thoughtfully. "Perhaps," he continued, "the helical structure of human DNA can be made to intermingle with the helical structure of our DNA." He began spouting hypotheses. Ivy had no clue what he was talking about, but the cloud of smoke around his head was getting larger.

"Marc," Mrs. Daniels called from the kitchen, "is something burning?"

Ivy and Mr. Daniels looked down at the barbecue. He quickly flipped everything over.

"I'd like you and Olivia to come down to V-Gen," he said. "My colleagues would be very excited to meet you. Of course," he went on in a low voice, "you should probably pretend Olivia doesn't know about vampires. Who knows how ASHH might feel about that."

"What's ASHH?" Ivy asked, waving Olivia over from where she and Brendan were playing death tag with Bethany.

"The Agency for the Security of Human Hybrids," Mr. Daniels explained.

"That sounds ominous," Ivy remarked.

"There have always been legends in the vampire community about the horrific results that ensue when a human and a vampire mate," Brendan's father said.

"Like how I used to have four heads?" Olivia interrupted.

Brendan's dad did a double take.

"She's joking," Ivy clarified.

"Of course," Mr. Daniels said sheepishly. "In any case, it's been a source of great paranoia. Vampires are terribly worried that a human and a vampire will produce some sort of monster, which might cause our existence to be revealed.

For this reason, ASHH was set up by the Vampire Round Table to investigate reports of vampirehuman relationships. It's all nonsense, of course," he said, "but ASHH checks into each and every tabloid headline about a deformed offspring. They're kept quite busy, as you might imagine."

"Have they ever discovered any actual hybrids?" asked Ivy. Maybe that's what Olivia and I are, she thought with a shiver.

"Not a single one," Mr. Daniels answered. "I personally believe ASHH isn't worth what it costs to run, but unfortunately I'm in the minority. And in any case they do do some good work - including funding a few projects for V-Gen." He leaned close to the girls. "It helps that the agency's office is in our building, but they do tend to poke their noses into our business more than I'd like."

"Do you think they have files about us?" Ivy asked apprehensively. Olivia nodded like she'd been about to ask the same question.

"If they don't already," Brendan's father said, "I expect they soon will. But don't worry," he added upon seeing Ivy and Olivia's reaction.

"Since you two being twins has become so public, ASHH wouldn't dare kidnap you for study."

Somehow, thought Ivy, that doesn't make me feel better.

"Um, Mr. Daniels?" Olivia said, gesturing to the barbecue.

Mr. Daniels quickly picked up Olivia's veggie burger - now charred and smoking - and dangled it in the air with his tongs. "Do you think this is done?"

Olivia's mom was planning to pick Olivia up from Ivy's house later, so the sisters decided to walk there from Brendan's. Most of the way, Olivia and Ivy didn't say much. Olivia was lost in her thoughts about what it would be like to have vampire parents. The Daniels were the first vamp grown-ups she'd spent time with. In some ways, they were just like normal parents. In others, they seemed much more . . . knowing.

As they climbed the long driveway, lined with bare trees, Ivy clicked her tongue thoughtfully. "What are you thinking about?" asked Olivia. "ASHH," Ivy answered. "About how maybe they're the reason there's no record of my adoption.

They could have covered it up."

"Why would they?"

"Maybe they were trying to bury my connection to a human sister," Ivy said, unlocking the front door. "For all we know, they orchestrated our split from the very beginning."

The thought sent a chill through Olivia. Her eyes took a moment to adjust to the dim lighting in Ivy's front hall, but her sister was already heading for the living room. Olivia hurried to catch up.

As they passed through the living room archway, Ivy stopped in her tracks, and Olivia walked right into her back. Over her sister's shoulder, Olivia could see the back of a black-suited specter standing in the middle of the living room.

It's ASHH! Olivia thought.

The man turned and looked at the girls sternly.

"Hi, Dad," said Ivy.

Ivy's father just stood there. He didn't even say hi. Finally, Ivy said, "Olivia, this is my father."

Olivia bounced over. "It's so great to finally meet you!" she said, but Ivy could see that her father's jaw was clenched. He forced himself to smile and, avoiding Olivia's eyes, shook her hand once before withdrawing. It was like he didn't even want to touch her.

Ivy's blood started to simmer. I can't believe he's being so prejudiced! she thought.

They all stared at one another until finally Ivy couldn't take it anymore. "Is it okay if Olivia and I use the computer?" she asked.

"No," her father dismissed. "I need it for work."

"It won't be for long," Ivy argued. "Olivia has to go home soon anyway."

"I have a great deal of preparing to do before we move, Ivy," he said abruptly.

Ivy's vision suddenly blurred. "I don't care about the move!" she shouted. "I care about Olivia. I care about my sister - unlike you!"

Her father's face changed, and his eyes flickered toward Olivia for the first time. "Ivy - " he began.

"I care about my real parents!" Ivy screamed.

Stricken, her father staggered backward, steadying himself against the edge of the couch.

"Sorry to bother you," Olivia said sadly to Mr. Vega as Ivy grabbed her hand and stalked out.