Disclaimer: None of these characters belong to me -- they all belong to Joss Whedon, and anyone else who's paid to play with them. I'm not one of those people, so please don't sue me.

A/N: Okay - sorry this has taken so long!! Aah! But see, this chapter is what I have been envisioning ever since I started this story -- and I kind of overkilled it in my mind, so that when it was time to write it, I didn't know how I was going to do it. I think this is up to the same standard as my other chapters, but... PLEASE tell me what you think -- this chapter, even more than the others, was hard to write, and I want to know if it holds up to the rest of the story.

Slight Warning: Like the title says, this is sort of a biology lesson -- so be warned, reproductive systems are talked about. And Spike makes one rather tasteless comment, so... But you knew Spike was sorta dirty-minded anyway, right?

Buffy lay on her back in bed, staring up at her blank, off-white ceiling, blanket clutched to her chest. What was she doing, agreeing to give Jonathan sanctuary? What if Warren and Andrew decided to come 'retrieve' him, maybe stop him from talking? How was she supposed to stop them? She couldn't kill them; they were humans. But she didn't want them to come after her friends or Dawn, in an attempt at ransom, or some other mundane villain-y idea they might have.

According to Jonathan, he did magic, Warren made any electronic devices - example: Invisibility gun - and Andrew summoned demons. They may not have Jonathan working with them, but just because they didn't use magic didn't make them any less dangerous; on the contrary, that made them even more dangerous - magic they could counteract, but demons were concrete, and had to be fought physically - and usually by her and Spike. And if they used the Invisibility gun, or Freeze ray gun again - or made a new one! - there really was no way to counteract it, until it had already been used. It was just a big waiting game. They had to wait until the Duo made their move, and only then could they make their own - and even then, they had to counteract whatever the two threw at them from scratch. It just wasn't a good thing.

A rapping came at her window, and she rolled over to see Spike peering in at her, a rakish grin on his face. She felt a smile tugging at her lips, for once glad for the distraction of this. She got up and unlocked the window, sliding it up so he could crawl through.

Now that everyone knew about them, she supposed they had to find other ways to 'live dangerously' - and what better way to do that than have sex in her bedroom, while there were several people sleeping in rooms connected to her own? Buffy grinned.

Life was actually starting to look up.

The next day was a Sunday. After some confusion due to Buffy wanting Dawn to get ready for school, Buffy, Dawn, Willow and Jonathan all made their way to the Magic Box. Buffy still wasn't entirely sure about the whole 'Jonathan' thing, but she'd told him she'd keep him safe, which pretty much meant she couldn't leave him alone. Since Warren and Andrew weren't vampires, her house wasn't safe, and neither was just standing out in the sun. Vampires were so much easier to deal with than humans. Well, anonymous vampires. Some vampires, who would remain named Spike, were a hell of a lot harder to deal with.

After their night of quiet-but-reckless passion, Spike had left a little before sunrise, telling her he'd see her at the magic shop for their daily dose of useless research. She tended to agree with him – they'd been researching the weirdness that was Buffy's pregnancy for almost three weeks solid, and had found nothing. Most slayers didn't even live long enough to get married – and why would they get married, if all they did was fight vampires? She was the only one they'd found who'd tried to have more than a superfluous social life, let alone a romantic relationship.

Huh. She was in a romantic relationship. With Spike. Out in the open, even. And despite the road bumps they'd encountered when she first told her friends about it, they were doing remarkably well – for him loving her unrequitedly. Even that part of their relationship had changed, a little. Since she was 'allowed' to interact peaceably with Spike in front of her friends now, and it was even encouraged (since they were under the impression she loved him), she found herself actually relaxing around him, at least a little. She was content. It sort of bothered her. But what worried her was the fact that she wasn't more bothered by it. It felt so. . . natural, and part of her was scared because of it. But mostly, she tried not to think about it.

Jonathan was silent as the group made it's way to the Magic Box, not really knowing what to do. He'd heard Buffy and Willow talking about research, but he didn't know what they were researching, and he really didn't think they'd want his help, anyway. He didn't blame them, either - they were right not to trust him. He'd been plotting against Buffy and her friends with two other psychopaths who turned out to be murderers. Or at the very least, morons. And he was one too, by association if nothing else. He was so dumb! Wanna take over Sunnydale? Okay. Idiot.

Spike was already there when they arrived, sitting casually at the round table, somehow finding a shady spot to sit, even with the front window letting light in all around him. He looked innocent enough, but the glare Xander was giving him said otherwise. Despite not even remotely liking Spike, Xander had tried to keep the anger to a minimum around the vampire, unless he did something to antagonize the young man.

Anya was putting some books away on the shelf, while Giles was just checking out a customer. After he'd left, the Watcher sank down into a chair beside Spike.

"Do we have to read through more books?" Dawn asked hopelessly, staring at the large pile of old books piled in the middle of the table.

Giles was about to answer her, when he noticed Jonathan hanging back behind the others. "Uh, Buffy?" he motioned Buffy over beside him. "What are you going to do about Jonathan?" he whispered.

Buffy frowned. "What do you mean? I'm gonna protect him from the other two."

Giles nodded, but elaborated, "I mean, while we're researching? He's bound to find out what's going on… with you, if he's aloud to listen in."

Buffy frowned at that. Giles was right, of course, but she wasn't sure what she should do about it. She had to be around Jonathan, but she really should help with the research.

Jonathan, already feeling slightly uncomfortable, noticed Buffy eyeing him and said, "Hey, I get it. You don't trust me. That's... well, not cool, but... I get that. I'll go sit in that back room and wait, I guess."

Buffy sighed. What was she thinking? He may have been a part of some horrible things the Trio had done to her, but... he was still Jonathan. She knew him. He wasn't some sleaze like Warren, who made a sexbot for himself, or some... well, she didn't really know anything about the other one, Andrew, but if he was anything like his brother Tucker, he was unstable to say the least. But this was Jonathan! The guy she'd saved from killing himself in the school's clocktower! The guy who, granted, cast a spell to make himself uber-cool and created a magical monster with the spell -- but when he'd found out the monster was linked to him, he'd ultimately chosen to do the right thing and give up his popularity, instead of staying perfect and letting the monster massacre people.

This was Jonathan. The guy who'd given her her 'Class Protector' award at Prom. Jonathan. She trusted Jonathan. Even when he did something incredibly stupid, in the end -- he always did the right thing.

Buffy sighed. She was gonna have to tell yet another person that she was pregnant. By a vampire. And with him, she'd have to explain how that was impossible. And no matter how many times she told it, it never got any easier. "Jonathan... There's something I'm gonna tell you, and it's gonna be weird, but..."

Jonathan frowned after Buffy explained what was going on. "So, let me get this straight... you and Spike slept together... and now you're pregnant, but that's not possible, because he's a vampire. So you're trying to figure out how it is possible... right?" The others nodded.

"See," Willow began to explain, "we really don't know what happened, but, this being Sunnydale and all... Well, we really don't know what we're looking for. Not a demon, which is really our strong-suit. We don't think it had anything to do with a spell, or the moon, or anything like that. But that doesn't leave us with a whole lot of other options. I mean, other than being invisible when it happened, there really wasn't anything weird--"

"Wait," Jonathan said, looking at Willow sharply. He turned to look at Buffy. "You were invisible?"

Buffy's eyes widened when she nodded. "Yeah, but... that shouldn't have done anything... right?"

Jonathan wiped a hand over his mouth, staring off into space as he thought frantically. "I... I don't know. Warren said something about... See, Andrew and me were fighting over the gun when it went off, so it wasn't a controlled blast that hit you. It was a, what'd Warren call it? A 'major dose of radiation', that caused your molecules to speed up. I mean, until you were turned visible again, you were like Spiderman, or something." He ran a hand through his hair agitatedly. He seemed to be talking more to himself now than the others, but they listened anyway, trying to follow his thinking. "Even if, if Spike was sterile, or the equivalent, anything that entered your body would have been affected by the radiation..."

Spike had a look on his face that was a cross between confused and worried. "Now, when you say 'entered'..."

Xander groaned and slammed his head down on the table. Spike rose an eyebrow at the display.

Jonathan didn't pay either of them any attention, running through the scenario rapidly. "Of course, the radiation was cancelled out when you became visible, but if the egg was already fertilized..."

"Of course!" Willow cried excitedly. Buffy looked at her in confusion. "Of course?"

Willow nodded to her, then looked back at Jonathan. "The radiation caused the sperm cells to mutate, becoming fertile. They would have become sterile again when she became visible, but if one of her eggs was fertilized before she became visible again, then there's no sperm to become sterile -- it's already part of Buffy, and no longer a foreign object!" She looked like she'd just figured out a very complex math equation -- in a way, it was, since they'd been working on this for three weeks now.

Her mood was dampened when Xander groaned and said, his voice muffled by the table, "Please stop talking about eggs and sperm! It's bad enough I know they're having sex!"

This made almost everyone blush, realizing they weren't talking about random biology, but Buffy and Spike's biology.

It was Anya who came to the rescue, clearing her throat and smiling happily at everyone. "Well! Now that that's figured out, I can go back to planning the wedding!"