Finally some explanations. I've had this planned the whole time, so it makes sense to me and I'm hoping it makes sense to everyone else. Disclaimers at the end.

The Tardis materialised right in the space between living room couch and kitchen counter. The Doctor walked out slowly.

"Where's Donna?" Buffy asked when there was no sign of the ginger-haired woman.

"She's just in the Tardis," the Doctor said while tilting his head back towards the box. "She's a bit tired after all the running and wanted to get some kip."

"Right," Buffy said. She sat down on a chair. The Doctor sat on the couch, leaning forward slightly. He didn't look the same; he had a look she knew well. The look of just holding everything together when everything was falling apart.

"How long has it been since I left?" she asked.

"Not long," he said trying to shrug off the heavy mood he was in. "You said something was wrong?"

Buffy gave a wry smile. "Yeah. Do you want to explain to me why I die and then come back to life moments later?"

"I'm sorry. I'm so sorry," he said.

"Did you know?"

"Yes."

"Since I first came into the Tardis?"

"Yes. The Tardis scanners showed that you were dead, and then you weren't."

"And you didn't think it important enough to tell me?" She couldn't keep the anger out of her voice.

"There wasn't really a chance. And I hoped that I was wrong, that maybe it would only happen the once. And I never expected you to leave so soon."

"So I really can't die?"

He shook his head sadly. "No. You're a fixed point, an impossible thing."

"But why? Am I even human? And why do I have this?" She handed him her mother's watch.

He took it, and his eyes widened when he looked at its front. "Where did you get this? Have you opened it?" There was panic, almost a touch of hysteria, in his voice, as well as a bit of hopefulness.

"I found it in a box of my mom's old things," Buffy said. She then told him about Willow's spell, the dream of her memories, her dream of her mother on the orange planet, her dream of the Tardis, and how her mother's voice had led her to a box and the watch. She then explained that opening the watch broke the spell over her, but nothing else happened—though the Doctor asked insistently if anything had. Buffy then brought out the box with the pictures and other memorabilia from her mother's past.

With one picture and the watch in his hand, the Doctor looked at her sympathetically. "This explains everything."

"What is it? What does it explain?" She looked at the picture in his hand; it was of her mother and an incredibly good looking man with blue eyes and a large smile.

He ran a hand through his hair, making it stand out at all angles. "Your mother wasn't exactly human. She was human when you were born, but before that—who knows how many years before—she wasn't. She was Timelady. That's what the fob watch means; it's part of this chameleon circuit… It can change a Timelord into a human. The Timelord consciousness stays in the watch, and while it's in there the person is completely human. If she had opened the watch she would have changed back to a Timelady. But you opened the watch, not your mother?"

"She died years ago, just before… I dropped in."

"Died? How?" he asked.

"She had a brain tumour. The operation was successful, but after…"

"An aneurysm?"

"Yeah."

"I'm so sorry."

"But if she was a Timelord… lady… what does that mean if I opened the watch? Is that why I can't die? But I opened it after I met you."

"No, it isn't why you can't die. It's part of it though, a piece to the puzzle." He paused and looked at her closely for a minute. "What about your father? Where is he?"

Buffy was taken aback for a moment. "I don't know. I haven't even thought about Hank Summers for a while. He walked out on us not long after I became the Slayer. He'd visit for a while, but then nothing. He never sent any help or called to make sure we were all right. I don't even think of him as my father any more."

"Is this him?" He held up the photo.

"No. I've never seen that guy before."

The Doctor seemed puzzled for a brief second. "I wonder. No, he has to be. It's the only thing that makes sense," he muttered. Again the hand ran through the hair and mussed it up even more. "The only explanation I can come up with is that your inability to die comes from your father."

"What?"

The Doctor rushed back into the Tardis. He left the door open, so she could hear him fiddling about and talking to himself. He came back out, waved his sonic screwdriver in front of her like some sort of scanner (which she was very tempted to hit away), and then went back in the Tardis. Out he came again, and once more sat on the sofa.

"This," he pointed to the picture and handed it to her, "this man can't die. He's a fixed point in time and space—just like you now. He's your real father."

"How… you can't know that." Buffy may not have thought fondly of Hank Summers as her father for many years, but that didn't mean she was ready to accept the fact that he wasn't her biological father. But one look at the Doctor's face told her that all the rushing about just then meant the Doctor did know it.

"I know this man. He travelled with me for a while, but he died, and I had this other friend—Rose—and she briefly had the power to bring him back to life. But she couldn't control it when she brought him back. That's when he could no longer die. That should not have been passed down to you."

"Then why did it?"

"The power in the heart of the Tardis changed him, and a Tardis is connected to the Timelords… That's it!" He spoke as if he was still putting it all together in his head, while at the same time dumbing it down a bit so he wouldn't have to explain it twice. "Both of your parents were technically human. But your mother still had hints of Timelord hidden in her genetic code, as well as certain energies not natively human. No scanner could have picked up any of it, but it was there. And your father was human, but energy from the heart of the Tardis and the time vortex itself keeps him from dying. It's only the combination of the two that allowed you to also become a fixed point."

"But I've died before I met you," Buffy said. "I drowned and a friend had to do CPR to bring me back. It wasn't like now."

"The portal you jumped into, the spatio-temporal singularity, acted as a catalyst. It activated the latent Timelord properties just enough to latch onto and ignite the energy from your father. Without it everything would have remained dormant, and you would be just another normal human being. Well, as normal as a vampire slayer can be."

"Never destined for normal, was I?" Buffy asked herself more than him.

"Ah, who needs normal?" the Doctor said with a slight, but comforting, smile.

"So the watch had nothing to do with anything?"

"Well… probably not, nothing noticeable anyways."

She looked at the photo again. Why didn't her mother tell her? If Hank wasn't her real father it would explain why the promised visits stopped coming, why he never came to look after her and Dawn when Joyce had died. But did her mother know? And who was this man?

"What's his name?" Buffy asked the Doctor.

"Captain Jack Harkness."

"I've heard that name before—Captain Jack. You mentioned him to Martha."

"They've met. He works for Torchwood… well, he is Torchwood now. He was in Cardiff last I checked."

This Captain Jack looked nice. They looked happy… but there was a certain age to his eyes. They were definitely older.

"Oi! What have you two been up to?" Donna asked as she just then came out of the Tardis. "Is everything all right now?"

"Yeah," Buffy said, putting the photo aside. "I just needed a few things explained."

"And he explained them? In words us humans can understand?" Donna voiced her usual ironic tone.

"Oi!" the Doctor said while looking a bit miffed. "Are you saying I'm difficult to understand?"

"You do tend to run on a bit," Buffy said.

"All those big, alien words," Donna added.

"Oh, it's just like you never left," the Doctor grumbled as the two women laughed.

"I'm starved," Donna said when they had stopped laughing. "You don't happen to have anything to eat?"

"I'll order some pizza," Buffy said.

"If you want pizza, I could just take us to the first restaurant in Italy to serve…"

Donna cut him off. "I don't want to end up in the middle of the Sack of Rome."

Buffy ordered the pizza with a smile on her face while she watched the Doctor and Donna argue over his driving skills.

After the pizza and stories about UNIT in San Diego, Donna took the opportunity to pull Buffy aside when helping her put the dishes in the dishwasher. The Doctor was out on the balcony.

"Is everything all right?" she asked.

"Yeah, I'm fine now." But Buffy hadn't missed that despite happy appearances, both Donna and the Doctor were a little down. "What about you? What happened?"

"Messaline," Donna said; her voice was soft which meant things were more than serious. "It was a planet that stupid box took us to all on its own. Martha was still with us. There was this war, with generated anomalies for soldiers. Kind of like clones. Just as we arrived they grabbed the Doctor and made a generated child from him. A daughter, Jenny. She had two hearts and everything. I thought he was just having a hard time becoming a dad, but he said he's been a father before. He didn't want to get close because he lost so much."

She paused, so Buffy pushed. "What happened to her?"

"He just started opening up, we were going to take Jenny along with us, but she was killed and never regenerated. I think it was like losing his whole family all over again… just when he got a bit of it back. We left, took Martha home, and then you called."

The Doctor then came back inside. "So, Buffy, are you coming with us again?"

Buffy took a moment to look at him. She now knew she was part Timelord, part of his race—not quite family, but close enough. Family was what they both wanted. But she still had family on Earth.

"I can't," Buffy said. "It's not that I don't want to. I do, really, I do. But… I want to meet my dad."

"You don't know your dad?" Donna asked.

"Not my real father, no. And I've just found out who he is. And then with Dawn pushing me away, I feel I have to have some sort of family to connect to. If it doesn't work out," Buffy looked at the Doctor directly, "I'll call."

"Okay," he nodded. "Need a lift?"

"With your track record?" Buffy asked jokingly. "No, I'll have to take care of things here first."

Donna hugged her. "It's not goodbye, so I won't say it. You better stay in touch."

"I will."

Donna walked into the Tardis.

"She's right. Why say goodbye?" the Doctor asked with a sad grin.

"Any last things I should know?" Buffy asked.

"No, I shouldn't expect so. Cardiff is in Wales…"

"Beluga or humpback?" Buffy asked.

"No, the country Wales, no h, not the mammaaaa-Oh, you're joking aren't you?"

"Yup, just keeping you on your toes. I'll see you around, Doctor." He turned to go into the Tardis. Buffy called out to him again. "Doctor, do you know who my mom was? Before she was human?"

"No, no I don't."

"But you and I could be related, right?"

"It's not impossible, but a bit unlikely."

Buffy nodded. "Till next time?"

"Yeah." He nodded with a smile and walked into the Tardis. Buffy watched as the engines started and the Tardis faded out of sight.

HXHXHXHXHXHXHXHXHXHXH HXHXHXHXHXHXHXHXHXHXH

Buffy's parentage was inspired by and taken from Life Past Death by jezaeiri on Twisting the Hellmouth. All things Buffy and Doctor Who do not belong to me, but to Whedon/Fox and Davies/BBC respectively.