"You know, Ferb, I'm actually glad you showed up," Phineas said, almost conversationally. "I think this would've been a little boring otherwise."

Ferb raised his weapon, a ray gun identical to Phineas's, in response, a determination in his eyes that Isabella had never seen in them before. The red-headed brother was unfazed, however, and merely continued talking as if they were all together in the backyard like any other day.

"You look quite cool in that pose, bro, like you're a hero protecting the romantic lead," he grinned. "It really puts your secret project in perspective. Anyway, are you sure you don't want to join me? I'm telling you, assassinations are even better than inventing things! You get to be so creative, and when you pull it off, it's… it's just such a rush-"

The motion-sensitive lights chose that moment to flicker off. Immediately Ferb fired a blast in Phineas's direction, the bolt casting a momentary green glow on the room. It collided with one of the pedestals and liquid and shards of glass sprayed everywhere, and as Isabella's mind registered what was happening Ferb pulled her into cover behind a pedestal.

The lights re-activated. Tentatively, Isabella poked her head around the pedestal, but Phineas was nowhere to be seen.

"I'll take that as a no, then," Phineas's voice rang out. Isabella quickly ducked her head back behind the pedestal she was taking cover behind as a powerful energy blast missed her by inches. Phineas and Ferb then began exchanging fire, one after the other, jars shattering and spewing their horrific contents of body parts and liquid everywhere.

"How about you, Isabella? We can be like Bonnie and Clyde, only, you know, hopefully with less death."

Isabella's heart skipped a beat. She'd fantasized long about being the Bonnie to Phineas's Clyde, but only ever briefly, in a romanticised Alternate Universe where the only thing that mattered was their mutual love. But hearing it proposed by Phineas as a real possibility was something different altogether.

She couldn't take it. To take it would be madness. Phineas was madness. But…

"If… if I accept," Isabella found herself saying, slowly. "Would you let Ferb go?"

There was a break in the exchange of fire as Phineas seemed to consider this. "Well… I suppose I could do that. Since it's you, Isabella."

The last few words sent an involuntary shiver up her spine.

"It's not him." Ferb's voice rang out among the silence. "It's not the Phineas we knew and loved."

The words were like a splash of cold water in the face, snapping Isabella out of the confused trance she had fallen into. It was like a switch had been flipped in her mind. Ferb was right. Of course Ferb was right. She had to do something about this.

Carefully, Isabella peered around her pedestal, watching Phineas poke his head around his cover to fire at Ferb before ducking back into safety again. Where before she felt a fluttering when she saw his face, now she felt only a determination to take that monster down.

She searched around her for a projectile, and her hands found a human heart. She grabbed it immediately, ignoring its slimy texture. The heart was much lighter than she thought. Her own heart started to beat faster in anticipation of her plan.

Phineas's face appeared once again. Pitching patch, don't fail me now, Isabella prayed. as she hurled the heart directly at Phineas.

It connected. For a second, Phineas turned, distracted, and Ferb seized the opportunity to fire a final stunning shot with pinpoint accuracy at his step-brother's chest. Surprise flashed momentarily on Phineas's face, then he slumped to the floor, finally still.

"Hey guys!" Phineas said cheerfully, from the TV screen.

"It's lovely to hear from you again, Phineas," Linda said. "It's like you're right here with us."

It had been a week since the government agents had come for Phineas. It had been completely without warning; Linda had come home, where two burly men in black suits were waiting, who informed her that their son was needed for a top secret government mission. Linda still scarcely believed it, and indeed wouldn't believe it if Phineas didn't call home regularly to assure her that everything was alright.

"Good job on the wiring, Lawrence," Linda added. "I didn't know you could get his calls to appear on the TV like that."

"Well, Ferb did it, really," her husband said bashfully. "I just supervised. Where is Ferb, anyway?"

"He's upstairs," Candace said. "Probably because he can already communicate with Phineas, by one of their dumb inventions. Or telepathy."

"We don't have telepathy, sadly," Phineas said. "But it's alright. How is everything back at home?"

...

[be aware it's been a week so far. replace searching of downstairs by what she usually does with Ferb (she reads). shuffle stuff around a bit.]

The nights were the hardest. Isabella no longer ended the day spent, yet happy, after a day of spending time with the Fireside Girls or Phineas and Ferb, and then drifting off to sleep with visions of Phineasland or new inventions. She now had to confront, alone, the memories of the terrible incident, exacerbated by the darkness, until she fell unconscious, out of exhaustion, where in her nightmares, Phineas continued to haunt her.

Not that spending time with people was any easier. She couldn't help but be suspicious of everybody, even the Fireside Girls, after learning that anybody could be a psychopath. She only spent time with a few people now. Her mother, for one. Pinky, too - though not technically a person, she knew Pinky had no secrets from her. And there was one more person.

Isabella strode through the door of the Flynn-Fletcher house, without ringing the bell. She spent most of her days here now, in the guest room with Ferb. Mostly, they did their own thing: she would get lost in a book, and Ferb would doodle or use the guest room computer to keep himself distracted. She quickly crossed the passageway and took the first step onto the stairs.

When she froze. Phineas was standing at the top of the staircase.

"Hey Isabella. How're you doing?"

The colour drained from her face. There was no way Phineas could be here. He was locked in a secure facility that Ferb himself had invented to keep him sealed away. He could call home, so that his disappearance could be explained, but if he was to escape, an alarm was supposed to alert Ferb and her immediately.

He began walking casually down the stairs towards her.

"Isabella, what's wrong?" he asked, in mock worry. "You look like you've seen a ghost."

Isabella blinked, and looked up at Candace's face. "Are you alright?" Candace asked again.

Isabella clutched her head, collecting herself for a moment. Candace as Phineas? What kind of hallucination is that? She exhaled the breath that she had unconsciously been holding in. "I'm… I'm fine," she managed..

Candace stared at her for a moment, worried. "Well if you say so. Ferb's in the guest room, if you're looking for him. Do you know why he's always in there?"

"Not really," Isabella lied.

"Shoot, I thought you might. Well, if he says anything, let me know." She patted Isabella on the shoulder sympathetically, then continued past her. The girl sighed and made her way up the stairs to the guest room.

Unlike Candace, she knew exactly why Ferb was staying away from his room. It had been hard enough for her to enter her own room again, given all the Phineas-worship stuff there was in it. She imagined it must've been doubly bad for Ferb, given that literally half the room belonged to Phineas himself. She knocked on the door of the guest room.

Ferb opened the door. His face looked gaunt, as if he'd aged several years in a couple of days. Isabella knew her face had similar features. They exchanged smiles. Ferb let her in and she slumped onto the couch, while Ferb resumed sitting at his desk. She allowed the feeling of serenity to wash over her, dealing mentally with the hallucination she had experienced minutes before, before picking up her book and continuing from where she left off.

Several hours later, the setting sun's red glow shone through the window. Isabella finished her book and sat up, then wandered over to look over Ferb's shoulder at what he was doing. The desk was covered in papers, blueprints that Ferb had drawn up to various levels of completion over the past few days. Even now, Ferb was doodling another idea for an invention, though he was barely focusing on it.

It was a huge improvement over how he had been a week ago. He would sit at the desk, pencil poised to draw, frozen in that position, as memories of him doing the same with Phineas overcame him. He'd remain that way until Isabella laid a hand on his shoulder and his body relaxed.

Yes, ultimately, that was the reason why she came over. Her presence soothed Ferb as much as Ferb's presence soothed her.

Isabella's eyes fell on a notebook, identical to the one in the mansion. It had spooked her at first, but now, after a week or so, her curiosity was stronger than her fear. She picked it up and flicked it open to a random page.

It was a sketch of her. In Ferb's handwriting, annotations filled the space around, detailing her likes and dislikes, habits and mannerisms. On the other pages were plans. Romantic dinners. Movie nights. A picnic for two, but on a rainbow instead of the ground. A trip to Niagra Falls.

"So this was your secret project," Isabella said. "Plans to get me and Phineas together. No wonder he was confused."

Ferb nodded in confirmation, and Isabella chuckled.

"Oh my gosh, he must've thought you had a crush on me! He really was oblivious right to the end, wasn't he?"

Ferb rolled his eyes, grinning, as if to say 'you have no idea'.

"Oh, I heard Buford got back home today," Isabella remembered. "And his mom said his diction and body odour have both improved."

This got a snort out of Ferb, which in turn caused Isabella to laugh. She hadn't had a proper laugh in what felt like an eternity, and it felt good.

"I really am chatty today, aren't I, Ferb? I think it's because you're just so good to talk to." She lay back onto the couch, thinking. "Phineas was right: it's not what you don't say, it's how you don't say it."

"And I'm British," he added, with winking.

She laughed, and for a brief moment, everything was alright with the world. But then reality kicked back in, and darkness gathered outside the window, waiting to attack them both once again."

"Hey Ferb?" Isabella said. Ferb turned to face her, inquisitively, in response.

"Can I sleep over here tonight?"

Without a word, Ferb left the room. Seconds later, he returned, with a pile of blankets, atop of which was balanced a tray of assorted goodies, chosen to accompany an evening tea.

"Crumpets or toast?" he asked.

*A few weeks later*

"Friends, zombies, Irving," Isabella said, Ferb beside her, to the assorted crew of people that had assembled in the backyard, which included the Fireside Girls, Buford and Baljeet, and their friendly neighborhood stalker. "We have gathered you here today to take part in an exciting project."

"Braaains?" Zombie Buford groaned in an almost hopeful tone. The Fireside Girls looked at him worriedly.

"Should we be worried?" Katie asked nervously, as the girls edged away from the zombified bully.

"It is quite alright, he is harmless," Baljeet said. "His vocabulary is highly limited, due to tinkering in the Broca's Area of his brain. Plus, he is technically Frankensteinian, rather than a zombie, although even more technically, since Frankenstein was the name of the inventor rather than the monster itself-"

"Laaame," Buford groaned, and he tried to take a bite out of Baljeet's arm. The Indian boy retracted his arm in disgust.

"Ugh, Buford! Did you not just hear me explain how you are a frankensteinian monster and not a zombie?"

"Saaame," he droned, shrugging.

"Anyway," Isabella said. "We've already ordered the parts, and they should be arriving any minute now."

"So we're building something?" Irving asked excitedly. "Ooh, I've waited for this day for so long! What're we building?"

Isabella hesitated, until Ferb held her hand tightly, reassuringly. She smiled.

"We're building a rollercoaster."