River watched sadly as Tanya went into the kitchen to talk to her brothers. So many innocent people lost, and this little family left to deal with it all. There were times like this that the universe was so unfair River just wanted to scream. She'd seen horrible things in her weird, crazy life. She'd been hurt and she'd hurt back, even killed those whom might not have deserved it. Someone so hardened should be used to unfairness by now, but River couldn't help wishing things had been different for Tanya and her family.

She hadn't even realized she'd sighed until the Doctor turned to her with concern. "Are you okay?" he asked quietly.

River shook herself our of her dreary thoughts. "I'm fine." She gave her husband a weak smile. "It's just, sometimes you find yourself thinking things were different, you know?"

Something sad sparked in the Doctor's eyes. He had to swallow a few times before he finally whispered, "Yeah, I know."

River felt a surge of sympathy for the Time Lord. Here he was confronted with a family which was the last of its kind. The kind of memories this had to be bringing back.

River laid a comforting hand on his knee, giving him a sympathetic smile. "It's not your fault, sweetie." The Doctor looked at her, a little surprised, but after a few moments he gave a small, grateful smile. They sat like that for a while, neither speaking, just taking comfort in each other.

Tanya led her brothers in from the kitchen. The twins hurried over to the couch, blinking curiously at Castle and Beckett, but John – Jonora – remained wary. "Tanya, can we trust them? I thought humans had rules about children living with adults." His voice was only slightly higher than it had been before, and a bit softer.

Tanya nodded. "There's only four of them," she pointed out. "They could have brought more but they didn't."

The Doctor gave the boy a cheerful grin. "Don't worry Jonora, I'm pretty well-known with all the alien-related agencies. I can make sure they won't try to lock you up."

Tanya looked at him, eyes narrowed thoughtfully. "You're not a cop." It wasn't a question. "Who are you again?"

"I'm the Doctor."

Ren and Irie looked up, eyes wide with wonder, while Jonora and Tanya blinked in surprise. "The Doctor?" Jonora asked in a voice tinged with awe. "From the stories?"

The Doctor looked amused at their recognition. "What stories?"

Tanya rolled her eyes. "It's not him, Jonora," she told her brother. "It can't be. It's just a legend. Stories the Time Agents at the bar used to tell when they'd had a bit too much to drink."

"Ooo, I love a good legend," The Doctor said with a bright grin. "Legends are always fun, especially when they're wrong." His expression sobered slightly. "But I really am the Doctor."

Tanya raised an eyebrow scornfully. "You're the last of the Time Lords? The man who saves universes?" There was no mistaking the mockery in her voice.

The Doctor flinched from the first part, but nodded. "Well, that's the idea anyway," he admitted.

"Then where were you?" Tanya's silver eyes were unforgiving. "When my home, my people, were taken, where were you? Hmm? The man who saves universes, where the hell were you when the Arondrians were slaughtered?!"

The Doctor looked stricken by Tanya's accusations. He shrunk away, his eyes far older than they had any right to be. Despite her sympathy for the girl, River felt a surge of protectiveness over her Time Lord. "He can't save everyone, Tanya," she said with a slight edge to her voice. "Some things can't be changed."

Something in Tanya's eyes wavered, and River felt a rush of sympathy. "I'm sorry Tanya, but there's nothing we can do. The war's over. But we can help you now."

The teenager hesitated, then sighed, still tensed uncomfortably. "You'd better," is all she said. Without another word she turned and strode off into the kitchen, Jonora following her worriedly.

Beckett turned to the Doctor with a shaken expression. Clearly Tanya's story had really impacted her. "Is there really nothing you can do?" she asked quietly

With a sigh, the Doctor shook his head. "I can't change an event someone told me about. It cancels out me being told about it... it's all confusing and timey wimey, but in the end there's nothing I can do." There was a defeated slump in his shoulders, and River hated the dull look of pain in his eyes.

Beckett seemed to gather herself up for a moment. In a firmer, serious tone she told the Doctor, "Then it's not your fault. Now I need you to focus now. This family needs our help. Now, what do you know about the Fatorins?"

Beckett's words seemed to shake the Doctor out of his stupor. He straightened, a thoughtful expression on his face, the mournful air of moments before gone. River was privately impressed with how Beckett had handled the Time Lord, even if the effect would only be a temporary distraction from his guilt.

"Fatorins aren't too different from humans," the Doctor said. "But they're a lot more stubborn. Once they get focused on something it's nearly impossible to distract them from it. They live on Akali for several million years after this." He frowned thoughtfully. "Never knew they stole the place, though. Doubt they remembered it themselves by the time I met them."

Castle perked up at this last part. "So you've met them before?"

The Doctor nodded. "In the 38th century. Nice enough place, if a bit politically driven. Not all that different from Earth. I'd heard of Raktor before, but apparently he was some big dictator they'd deposed not too long into his reign. He'd faded into legend long before I'd arrived. The government when I met them was closer to a democracy."

"Did they have that Tyron Energy thing?" Castle asked curiously. "I thought you said no one had that for years and years."

The Doctor looked almost guilty. "Erm, yeah, I did say that. And most people don't find tyron energy for quite a few years. But Fatorins and a few other species were slightly ahead of the curve on that one.

River rolled her eyes. "So this whole time we thought we were tracking a time traveler and we're really after a technologically advanced alien?" she asked with a pointed glare.

"Well, I can't be right every time!" the Doctor defended himself indignantly.

Beckett rolled her eyes at the Doctor's forgetfulness, but the look was gone in a moment and the focused detective was back. Calmly she asked, "What do they look like?"

"They're pretty much human-shaped, but they've got dark brown skin, a scrunched up nose like a hog-nosed bat, and little cow ears that stick out from the sides of their head. Oh, and no hair. Kinda wrinkly. Yellow eyes."

Castle frowned. "Alright, so they're not going to blend into a crowd easily."

The Time Lord shrugged. "There are plenty of ways to look human. They could have a shimmer or be wearing a human suit." His look faded into a reminiscent one. "Or they could have a perception filter like those sexy fish vampires."

Castle and Beckett looked a little taken aback. The writer seemed on the verge of asking more, but River cleared her throat. "As fun as that story sounds," she said smoothly, "can we get back to business? The question now is how do we find this Fatorin?"

"Find and question," Beckett stated firmly. The detective's gaze was fixed on the gun still in River's holster on her hip. Clearly, she didn't trust that the time travelers weren't planning on killing the culprit once he was caught.

River gave the detective a brief nod. "Find and question," she affirmed. Beckett seemed to relax, before throwing herself back into what River was increasingly recognizing as her 'detective mode.'

Castle leaned forward, hands clasped thoughtfully. "So," he summarized, "we've got an alien killer on the loose who may or may not look like a completely random human and may or may not be planning an invasion?"

"Pretty much, yeah," the Doctor said breezily. "But don't worry, we'll find them."

Beckett scoffed, "How can you be sure?"

The Doctor smiled, jumping to his feet with sudden energy. "Because I'm the Doctor," he said with a smug grin. "If there's one thing in the universe I'm good at, it's finding trouble. Now!" He clasped his hands together eagerly, a manic grin on his face. "We've got to track down an alien with possible transport off this planet, a flaming sword, a possible disguise as a human, and has a deep, murderous grudge against a family of aliens disguised as humans. So where do we start?"

Beckett spoke rapidly. "If they're disguised as human, they've probably got falsified records like Tikrah..."

"... but if they look like aliens they'll be trying to hide somewhere they won't be noticed," Castle continued, picking right up where his partner had left off. "Somewhere secluded..."

"... like that parking lot we found Tikrah in!"Beckett realized, not missing a beat. "The area around there was too open for them to get anywhere without being seen during the day..."

"... and we were there that night..."

"... so unless it left after we left that night..."

"...or before the body was found..."

"... it's still there!" Beckett finished triumphantly.

They turned to the time travelers with triumph, only to see the Doctor blinking bemusedly at them and River snickering quietly. The confusion on the partners' faces only made her laugh harder. "Ooo, that's a fun trick," she remarked, still snickering. "I think I'll have to learn that one. What do you think, dear?" She turned to her husband with a smirk.

The Doctor blinked a few more times before shaking his head. "Humans," he snorted.

River just rolled her eyes. "So he's most likely at that garage, but he could have disguised himself to be human."

"Maybe, but I don't think he did," Castle responded. "Tanya said she'd seen him in Fatorin form."

"Maybe he hadn't activated his shimmer yet," River argued. "Or maybe he was just giving her a warning."

Beckett's brow furrowed. "Yeah, but why would you warn someone you're hunting down?" She mused.

The Doctor perked up. "Unless they weren't hunting them down," he reasoned. "Just coming here to hunt down one little family seems pretty pointless. They've already got the whole planet, haven't they? Maybe they needed something from Tikrah."

"Yeah, but what could they want with him?" Beckett asked. "They destroyed his entire species, what would they need him for?"

The Doctor shrugged. "Could be anything, you know, maybe there's environmental problems with the planet or something, or there's a resistance they think he could stop, or maybe there's more than one Fatorin and this one was trying to warn her."

Beckett stood, soon followed by the rest of the team. "So he could still look human. I'll get Esposito and Ryan to check out the security footage for outside the garage, see if there's anyone there who might be our guy. Doctor, you were able to tell last time that the aunt's records were fake. I need you at the precinct so you can check out files of people on that security footage. River, he doesn't have any clearance without you there, so go with him. Be careful if Gates shows up, Ryan and Esposito aren't the best liars, so help them if you can. Castle and I will check out that parking garage."

The Doctor looked surprised for a moment, then nodded. "Alrighty then." He gave his wife a quick smirk. "Come along, Pond," he joked lightly as they headed for the door, leaving Beckett and Castle behind to say goodbye to the Karrow family.

River was a little surprised at the dynamic they'd fallen into. Usually it was the Doctor taking charge and the human companions following what he said. But the detective was clearly experienced and clever and used to giving the orders. Castle was her partner, yes, but she was the one with actual authority. It was natural for her to take charge of her own investigation.

More surprising was the way the Doctor was doing what he was told. The Time Lord had never exactly been big on authority or following orders. Then again, it wasn't like he was just bowing his head and letting her take over. They had been bouncing ideas back and forth, and she was trusting them on the matter of aliens and time travel. Still, it was an odd situation, and one that she might have to tease him about later.

If he can remember it, she thought sadly.

SCENEBREAK

Beckett turned to Tanya, who was still glaring at them with mistrust and doubt. She lowered her voice to sound as reassuring as she could. "Don't worry Tanya. We're going to find who did this."

Tanya just snorted disbelievingly. "Yeah, you'll find them alright," she agreed. "Then they'll kill you, just like they killed Tikrah. They've got technology like you wouldn't believe."

"We'll be fine," Beckett assured her. "We've been trained to deal with things like this. We've got guns, and we can handle a guy with a sword." Privately she was worried about their chances against the Fatorin. She wondered whether she should have kept River with them to have another gun hand, but she and the Doctor were needed more at the precinct. There was no way to call in back-up without things getting awkward, and if the alien was still at the garage they needed to check it out as soon as possible. It would have to be the two of them.

Tanya just shook her head. "You better hope it's just a sword," she said ominously.

"Hey." She waited until Tanya finally met her gaze again. "I promise you, Tanya. We're going to find them. I will not let this go unsolved. Alright? And we're going to make sure your family's safe."

The teenager measured Beckett's gaze, eyes going wide with surprise. "You actually care, don't you?" she asked quietly. "You actually care about avenging Tikrah. Why? What does it matter to you?"

Beckett closed her eyes as fresh memories flooded her mind. A man in a parking lot faded into a woman in an alleyway. Opening them again, she gave Tanya a sad smile. "Cause I've been in your place, and I know how it hurts," she explained simply.

Tanya blinked in surprise at Beckett's sincerity, then sighed sadly. "I'll hold you to it then," she said quietly. "Help me keep my family safe."

"I will," Beckett promised solemnly. With that, she and Castle said good-bye to the boys and headed out to the car.

Castle seemed to notice how quiet his partner was being. "You okay?" he asked with concern.

The detective let out a breath, the depth of their situation hitting her. "I promised her we'd catch the guy, but what if we can't?" she confided quietly in her partner. She wouldn't have said it with River and the Doctor around. But she could tell Castle anything. He always understood, and he always knew just what to say to make it better. "What if River's right and we're way in over our heads?"

After a few solemn moments to show he understood, Castle gave her a reassuring smile. "We've been outnumbered before and gotten out okay," he reminded her. "We'll be fine with one alien."

"And what if it's not just one?" Beckett argued quietly. "What if there's an entire invading force, Castle? This isn't like anything we've dealt with before."

Castle shook his head calmly. "You know that's not true. This is a murder investigation. It always has been. Someone's died and it's our job to find out who. And from what River was saying, the Doctor's gone up against armies before and won. He can do it again." His grin turned lopsided as he joked, "The combined forces of the Doctor and the great Detective Beckett. The world won't know what hit it."

Beckett cracked a smile, her fears fading as she thought about what Castle said. He was right. They needed to focus on the murder, and if it turned out to be bigger than that, they'd deal with that when they got there. "You're right," she said with more confidence.

"Oh, that reminds me," Castle said cheerfully, clearly trying to drive the conversation away from the solemn turn it had taken. "I haven't said 'I told you so' yet." The childish light gleamed in his eyes again. "For once I was completely, one hundred percent right. I so called the Doctor being a time traveler!"

The detective laughed at her partner's antics. Her chest filled with warmth. He always knew how to make her smile. Instead of responding, she just rolled her eyes. "Come on, Castle. We've got an alien to catch."

SCENEBREAK

Back at the precinct, as the Doctor scanned through the files with his sonic screwdrivers, River had turned her attention to the other partners. Esposito and Ryan still seemed to be coping with the revelation of aliens, but like Beckett they seemed to be forcing themselves past it and throwing themselves into the case. But unlike their leader, that didn't stop them from asking questions.

"So, how's it work? Time travel, I mean." Esposito was leaning forward with his hands clasped, his curiosity clearly outweighing his unease. Beside him, Ryan looked just as curious.

River laughed quietly. "That's a question for the Doctor I'm afraid. And he doesn't really like to explain that one." She turned to glance at the man in question, who was scrolling through the computer files with his sonic screwdriver whirring relentlessly. She turned back to the two men with an easy smile. "He says it's because it's way above human comprehension, but I think he just doesn't want to explain the thing that makes him look impressive."

"Is not," the Doctor interrupted sullenly from his spot by the computer.

River rolled her eyes. Without looking at him she scolded lightly, "Focus, dear." She smirked at Esposito's bemused expression.

Ryan, however, was focused more on his next question. "But what about changing events? Like, doesn't changing a small thing make ripple effects that change the future?"

Oh, this one she could answer. She leaned back thoughtfully in her chair. "Not exactly. And not everything in the future is set in stone. Most of time is in flux; anything can happen. And the universe will mostly work to compensate for any small changes, rearranging itself so the future turns out more or less the same. So we're mostly safe changing things in the past. But there are some points which are fixed. They can't be altered, they always happen the same way. The Titanic, Pompeii, Hitler's death. Interfering with events like that could tear the universe apart."

Ryan looked thoughtful as he processed what River had told him. Esposito took his turn to ask a question. "So what's the future like?"

River raised an eyebrow. "Depends on what year you're asking about. I live in the 51st century. It's pretty nice. Though security guards are rubbish there. Cute enough though."

Esposito looked surprised. "Security guards?"

"Oh, did I mention? I live in prison." River explained with a smirk.

Ryan and Esposito seemed a bit taken aback. "What for?" Esposito asked guardedly.

River flinched as she remembered watching her own crime only a week before. Knowing that the Doctor had faked his death hadn't made it any easier to watch. That doubled with the memory of pulling the trigger herself...

The archaeologist shook herself out of her thoughts. "Doesn't matter," she said quickly. "I'm innocent, sort of, I just stay there cause this idiot," here she threw a pointed glare at the Doctor, "needs me to. I get out often enough, and it's not a bad place to live."

Esposito still looked a little suspicious, but Ryan seemed more interested in River's story. "So is police procedure still the same? How do the prisons work?"

River was about to answer when the phone on that partners' rang. Esposito picked it up swiftly. "Esposito," he greeted. He listened for a few moments, then held the phone out for River. "It's for you," he told her.

River took the phone. "Yes?"

"There's nothing here." Beckett's voice had a slight edge. "We checked the whole place, there's nothing. Not a trace. He must have gotten out right after the murder. We've got nothing."

River made a disappointed sound in the back of her throat. Esposito and Ryan looked at her curiously, but she ignored them. "We haven't found anything here either," she told her. "The Doctor's still looking through the files."

Beckett sighed. "Of course not." There was a long pause, then the detective spoke again. "Listen, it's late, we should get some sleep. Castle says you can stay at his place as long as it takes to solve the case. Just grab a cab and head over." The line was cut off, leaving River to deal with a sudden rush of frustration. Usually adventures with the Doctor were so whirlwind that it was hard to keep up. The way this case was dragging on frustrated her to no end. It was all brainwork, this detective stuff. All this waiting around.

Oh well. Work to be done.

River turned to her husband. "Come on sweetie," she said as she stood. "We'll keep working tomorrow."

They'd work as long as it took.

Urgh, I sort of lost steam at the end, but I think the rest is sort of okay. Blegh. I'll try harder on the next one. Anyway, have some mixed River and Beckett POV. And some Esposito and Ryan awesomeness.