Danny, Sam, and Tucker walked down the hall surrounded by the cheerleading squad. Normally, that would have caused the day to qualify for "best in his life," if not for one minor detail.

Fiona Fenton, his new archenemy. She chattered happily at him about nothing, completely ignoring her fan club. It was as though she was trying to make up for the night before. So far, she had only succeeded in reminding him why evil ghosts needed to be vanquished as quickly as possible.

He found himself praying that she was a ghost. It would have made life so much easier.

"Like, what is up with these lights?" asked one of the girls. She may simply have been trying to get Fiona's attention, a feat that was doomed to fail. She did, however, succeed in drawing Danny's gaze to the ceiling above. The lights flickered and pulsed as though possessed by a foreign entity. He grinned and turned to his friends.

"Hey, guys, I've got to be somewhere," he muttered.

Sam, whose attention was more on Fiona, nodded vaguely. "Sure. See you, Danny." Tucker didn't even bother to respond.

"Maybe we can all come with you!" Fiona announced, clapping her hands in delight.

"Uh, maybe later," the boy said quickly. He practically ran out of the school to get away. Outside, he glanced around, finally locating his target as she appeared in a shower of sparks next to the wall. "What's going on?" he asked brightly.

Kat rubbed her eyes and blinked several times. "Well, dang! I was going to say you're out of luck, but…" She shook her head and sighed. "I assume that was miss twin sister." At Danny's nod, she went on. "She doesn't look a thing like you from my point of view. She's got the same basic shape, but her EM signature is completely different."

"Her what?"

"Electromagnetic," she answered, waving her hand dismissively. "Listen. There's nothing like that thing in the Ghost Zone, so I don't think it's a ghost. But it's not human, either. No human is that bright. Even you're not that bright."

Danny momentarily considered making a crack about her intelligence, then decided against it. By the look on her face, a joke would not be welcome. He shrugged. "Great! So that means I can kill her."

Kat opened her mouth as though to speak, but closed it again as she thought better of whatever she'd been about to say. "There you go again," she sighed. "Jumping to conclusions. I'll beg you to recall that nonexistant morn on which you claim we first met."

It had actually been about 3:30 in the morning in the school auditorium. Danny had threatened to send her back to the Ghost Zone, and had gotten quite a lecture on not being the first to attack non-hostile entities. He looked down at his feet in mild annoyance until he remembered something else. "That was in the Nasty Burger, I think," he pointed out insolently. "You were pretending to be a normal human."

She mock glared at him for a second. "Bite me. Cheerio, Phantom. Don't forget about rehearsal tonight."

"Have I ever forgotten?" he demanded of the fading blue smoke that heralded her overly theatric departure. With an aggravated huff, he turned to go before Fiona could catch up. It was a nice day; he decided to work on his homework in the park rather than go home and deal with his "sister's" lack of presence. He didn't like the way his parents acted when she wasn't around. It was easy for Kat to say that he should find out what Fiona wanted before he attacked her. It was completely different to see everyone he knew acting so hypnotized.

Lost in his thoughts, he didn't pay much attention to where he was going until a voice yelled, "Bugger it, anyway!" and a few sheets of paper fluttered past his feet. He retrieved them, then helped their owner reclaim the rest of her lost work. "Thanks," the woman said as she stood and took the proffered pages. She smiled nervously, brushed short, brown hair out of her eyes, and adjusted her black-framed glasses.

Danny smiled back. "No problem."

The woman had to have been in her early twenties, but she blushed a shade of bright red not found in nature and shuffled away, hunched over slightly and looking almost like a girl half her age. He could hear her muttering to herself, something about a blatant plot device. He dismissed the meeting from his mind and returned to the current dilemma.

Fiona Fenton. Perfect Fiona Fenton. Fiona who could do no wrong. It was disgusting.

What if he was just jealous? What if-

"I am the Box Ghost!"

Danny cringed at the proclamation shouted practically in his ear and whirled angrily. "Didn't I send you back to the Ghost Zone yesterday?" he demanded, switching to ghost mode.

The slightly mad spook in coveralls grinned in what he probably thought was a malicious manner. "It is true that you trapped me in your cylindrical container and sent me back! But I have come back to-"

He was suddenly interrupted by a beam of light as Danny trapped him the Fenton Thermos for possibly the third time in as many days. "Where do you keep coming from?" he muttered, more to himself than his prisoner. He was relatively certain the Box Ghost hadn't come through the Fenton Ghost Portal, and the one owned by Vlad Masters was too far away to make the trip that quickly.

The boy glanced around to make sure he was alone, then changed back into a human. He knew some ghosts had the ability to tear holes in reality and go back and forth; maybe Box Ghost was one of them. Stowing the thermos in his backpack again, he continued on his way across the park. Behind him, a squirrel chattered curiously as it watched him go. That was a very interesting ability Danny had, it thought. It shimmered and grew larger, changing color and form until it had become Fiona Fenton.

She smiled slyly. A very interesting ability, indeed.

Rehearsal for the annual Casper High school musical tended to be haphazard at best. The Phantom of the Opera was scheduled to be performed in just over a month, and it did not look like they would make that deadline. The small volunteer orchestra couldn't play even half of the score; the actors kept forgetting their lines; and the props were laughable.

Fiona had insisted on accompanying Danny to the auditorium, which meant the poor drama club had quite a sizable audience. They were very nervous, but at least they hadn't started fawning yet. Instead, they stuttered and stammered and tripped and sang horribly off-key. Finally, the theater director called for a short break.

Danny slid down the ladder from the catwalks to the stage and sauntered over to join Kat. She was already deep in negotiations with the director to ban the audience. For once, he agreed. While he went to order the Fiona Fan Club to leave, Kat rubbed her eyes and turned to Danny.

"You know," she said wearily. "Normally, I would say having an audience is good for them, but that girl's EM field is giving me a headache. It's hard to think."

"She's got them all hypnotized," Danny murmured.

"There could be any number of reasons for that. It doesn't mean she's bent on taking over the world."

"You're sure she doesn't have you hypnotized?"

Kat opened her mouth to refute, then closed it again thoughtfully. She was infuriatingly egotistical, but she was also an intellectual. It may have galled her to think that she could be hypnotized, but she was too smart to reject the possibility out of hand. She opened her mouth again, and was interrupted by the theater director's call for places. She closed her mouth with an audible click of her teeth and let her eyes flash green in anger, something she had picked up from Danny.

The boy snickered as he clambered back up to the catwalk, or as Kat called them, the flies. She said it was an old term, which he had replied to with a dubious expression. He glanced out into the seats to see that Fiona had charmed her way into being allowed to remain. Doubtless, Kat was not pleased, although it was impossible to tell while she acted. She was, above all, a professional. While she not may not have the greatest actress in the world, she certainly wasn't going to let a minor irritation like that color her performance.

At least, not as such, but the flickering lights and white noise from the speakers betrayed her mood. Danny resisted the desire to call down and tell her to relax as the spotlights began to spark. Doing so would lead to awkward questions, and it wasn't doing any actual harm yet.

When rehearsal let out, he walked out with Kat. "So, you were saying?" he began.

"That was so cool!" squealed Fiona as she ran to meet them, interrupting Kat again and angering her further. There was nothing she hated more than being interrupted, although Danny's twin probably came very close.

"'Cool' is hardly the word one should use to describe such a brilliant work of art," the haughty thespian rebuked. "The Phantom of the Opera is one of the greatest love stories of our age, and you cheapen it with your irreverent vocabulary."

Fiona narrowed her eyes and muttered something unintelligible. Danny thought she looked somewhat shocked beneath her affronted expression. In fact, it suddenly occurred to him that she had the same almost bewildered look in her eyes that she wore whenever she looked at him. It was as though she didn't know what to do with someone who wasn't under her spell. He filed that away for future reference and said goodbye to Kat, who had materialized her top hat from out of nowhere and stalked off in the opposite direction.

It was actually quite a while before he realized that Fiona wasn't chattering endlessly like she usually did. He may have continued to not notice if she hadn't suddenly said, "Hey, Danny?" She almost sounded shy.

"Yeah?" he responded, not really interested.

"Um…I just wanted to say that I know about you." Danny froze, hardly daring to breathe. She couldn't possibly mean… "It's okay, you know," she went on, somewhat bolder. "I'm a halfa, too."

He stared at her. It had been months at least since he had last heard the term, and he was kind of slow to place it. Once he did, he continued to stare, unable to formulate any kind of coherent response. Finally, he said, "I have no idea what you're talking about." Inwardly, he cringed. That had not come out quite as strongly as it had sounded in his head.

Fiona giggled in that nerve-grating way that she had and transformed. It looked the same as when Danny transformed: two blue rings that passed across her body, changing her from a human into a ghost. He was torn between excitement at the prospect of someone else like himself who was actually on his side, and distaste that said someone was Fiona Fenton. Then he really looked at her.

White hair, green eyes…she could be excused for that; they were supposed to be twins, after all. It was the black jumpsuit with white gloves and boots that caught his attention. No, it was just too…contrived…

He debated acting scared, then realized that too much time had passed for that to be believable. Instead, he folded his arms and leaned back slightly. "And you really expect me to believe that you're half ghost?" he asked skeptically.

Again with that confused look. She quickly covered it up with a bright smile, but her squeal seemed a bit strained. "Of course, silly! What else would I be?"

"Uh, I don't know. A full ghost, maybe?"

Danny was suddenly struck by an epiphany. Fiona had expected him to believe her completely; that fact that he questioned her was not only confusing to her, but worrying. Once again, she smoothed her expression, this time with an exaggerated pout. She grabbed his hand before he could draw away and attempted to smile disarmingly into his eyes. "You're my brother," she reminded him. "I would never lie to you."

"Unless you're not who you say you are," he pointed out.

For just a split second, those eyes were filled with rage, then blue rings passed across her again and the moment was gone. She sniffed sorrowfully and turned away, still holding his hand in one of hers. "I just want to live here with you," she said quietly. "You're my family, and I love you all. But I won't force you to believe me if you really don't want to."

Danny finally managed to extricate his hand from her grasp. "Look, just tell me how you got to be half ghost, and I'll consider believing you."

She was blatantly surprised as she turned to face him again. "I was born this way, of course."

The boy started to inform her that her story wasn't even remotely possible when he was suddenly struck by how abysmally bad an idea that would be. She didn't know he hadn't been born that way; clearly, she hadn't done a lot of research into his life before invading it. The fact that he might be able to use that in some way would occur to him later. For the moment, he was more concerned with the look of pure rage he had seen in her eyes. Even Kat never got that angry, and she had the shortest temper of anyone he had ever met.

He was still trying to figure out how to respond when she smiled again and squealed, "You need to think about it for a while. I understand! This is all so very sudden for you, and that's okay! It was pretty sudden for me, too! But now we both know we're not alone in the world!" She captured him in a tight embrace, then broke away to skip ahead, leaving Danny to follow at a slower pace.

Kat was not going to enjoy hearing that she was wrong.