1) While I usually write for Doctor Who and have tried to make this accessible for members of both fandoms, this is from the BAU's point of view, so it probably helps to have seen at least a couple episodes of Criminal Minds.

2) To preserve the integrity of both canons, this assumes that the Doctor's universe has an alternate BAU which is essentially the same but exists in a world with the Battle of Canary Warf, etc, and no BBC show called Doctor Who.

3) Set after Journey's End for the Doctor, and shortly after Memoriam for the BAU. That means no JJ, which is unfortunate, but that's the way the timelines worked out.

4) I own neither Doctor Who nor Criminal Minds.


Supervisory Special Agent Aaron Hotchner was not a superstitious man. He did, however, have enough sense and experience to know that certain things did not bode well for the near future. Calls from blocked numbers were disquieting. Haley waiting for him with crossed arms and a tapping foot was nerve-racking. Any member of his team coming to him with an expression which said "please don't kill the messenger" was alarming.

Section Chief Erin Strauss waiting for him in his office was . . . worrying, with a dash of irritating. It didn't have the same undertones of mortal peril as many aspects of his job did, or the emotionally draining potentials of Haley's wrath, but it did mean bureaucracy and politics and a number of other headache-inducing things.

At least she wasn't alone, which meant that this probably wasn't part of her ongoing attempts to dismantle his team. There was another woman with her – mid-thirties, dark, short-cropped hair, a nose a Roman would be proud of, and a feminine figure which wasn't quite hidden by her military posture and unfamiliar uniform. Some foreign military, perhaps? There was something vaguely exotic about the olive tone of her skin and the shape of her eyes.

"Chief Strauss," Aaron greeted with a nod as he entered his office.

"Agent Hotchner," she returned, all stiff professionalism. "I'd like to introduce you to Captain Ruth Stewart. Captain Stewart, this is Aaron Hotchner, unit chief of the BAU."

"Pleased to meet you, Agent Hotchner," Stewart said, brisk but not unfriendly. Flawless English, no accent. Probably not foreign, then.

"And you," Aaron replied, accepting her firm handshake. Confident, in control, nothing to prove. Good.

"Captain Stewart is from UNIT," Strauss explained. "She has requested that the BAU consult on a case. I've agreed."

Aaron did his best to conceal his surprise. He hadn't thought that UNIT ever cooperated with other agencies, much less asked them for help – and for good reason.

"All due respect, Captain Stewart, we study human behavior. Unless you have a personnel problem . . ." Though even then, he wasn't sure. Did UNIT employ aliens? Reid would know. He'd ask the young agent later.

"We have a human killer," Stewart stated. "Alien victims. Our usual methods are failing us – we were hoping that you could offer a fresh perspective. It's imperative that we put a stop to this before word leaks out to extraterrestrial population on a whole."

Aaron glanced at Strauss, and knew that it would not be wise to fight her on this. He turned his gaze back to Stewart.

"We'd be glad to help."

Well, Reid would be happy.


"I don't believe that there are aliens. I believe there are really different people." – Orson Scott Card


Derek Morgan flipped through the file he had been given. He flipped through it again. He looked at his boss, who ignored him steadily. He flipped through the file once more, just in case he had seen wrong the first two times.

He hadn't.

No wonder Hotch had waited to brief them until they were all on the jet. He had probably been worried that they wouldn't agree to come, otherwise.

"You're kidding," said David Rossi incredulously, stating what they were all (with the possible exception of Reid) thinking. "Aliens?"

"It's not exactly a foreign concept," said Hotch, who had obviously had plenty of time to come to terms with this himself. "Not like it would have been a few years ago. None of us can deny that they exist, or that they visit Earth."

He was right, of course. What with Canary Warf and President Winters' assassination and the latest event which had come to be known as "the Stolen Earth Incident," it had become common knowledge that aliens not only existed, they were advanced and ruthless and damned terrifying. Suddenly every law enforcement agency was giving lectures on how to recognize possible alien activity, and some of the more progressive colleges and universities were offering courses on xenobiology and the like. Still . . . .

"Hotch, this is insane. We don't know anything about aliens. Most of us don't know anything about aliens," he clarified quickly, as Reid opened his mouth. Dr. Spencer Reid was a genius, with several PhDs at the ripe age of twenty-seven, and seemed to know everything about everything.

"We'll learn," said Hotch. "At the moment, we're assuming the unsub is human, and a member of UNIT, given his knowledge. It's a case just like any other." If he doubted his own words, he gave no outward indication. "He seems to have access to UNIT's records and has been targeting relocated extraterrestrials in the LA area. Specific cause of death hasn't been determined, but there are small puncture wounds in the necks of each of the victims. I think it's safe to say that they were all injected with a toxin of some sort."

"Okay," said Emily Prentiss. "So we start with victimology."

"They're all aliens," said Derek. He was stating the obvious, but that was part of the point of these discussions. A lot of the time it was something painfully simple which cracked the case.

"Could be a hate crime," Prentiss suggested.

"Could be," Hotch agreed, "but let's not get ahead of ourselves."

"They're not just aliens," said Reid. He was flipping through the crime scene photos, but Derek was sure that it was more to have something to do with his hands than because he really needed to look at them again. Photographic – oh, sorry, eidetic – memory and all that. "They look alien," the boy-genius continued. "None of them are humanoids."

"So?" asked Jordan Todd. She wasn't really a profiler; just the interim media liaison while JJ was on maternity leave, but it could be useful to get an outsider's perspective. "Couldn't it just be a coincidence? I mean, how many aliens look human?"

"You'd be surprised, actually," said Reid eagerly, sitting up a bit straighter. "A wildly disproportionate number of registered sentient species are externally similar to humans, some of them nearly identical, right down to the coloring. Xenobiologists call it parallel evolution, but there have been theories about a common ancestor; some ancient species which achieved interstellar travel millions of years ago but has since suffered some sort of calamity or simply devolved –"

"Alright, so not a coincidence," Derek said, cutting across the ramble before it could disintegrate into Star Trek references. "Could be that he can't bring himself to kill anything that looks human."

"It's possible," Hotch agreed.

"We know that unsubs dehumanize their victims," Prentiss remarked.

"The fact that these victims aren't human would just make it that much easier," Rossi added.

"We need more information," declared Hotch. "Dave, when we land you go with Reid, Prentiss, and Jordan to UNIT headquarters. Talk to the experts; find out if there are any other commonalities between the victims. Morgan, you and I will go to the latest crime scene and a get a better grip on the methodology. There's more to this than meets the eye."


The crime scene was in an ordinary suburban neighborhood. It was the last place most people would have expected to house a reptilian refugee from the planet . . . something unpronounceable by humans. Which, Aaron supposed, was exactly why UNIT had chosen it for that purpose.

The entire street had been cordoned off and was crawling with UNIT personnel. Captain Stewart met them at the perimeter and waved them in.

"We had to clear the area of civilians, for security reasons," she explained as they strode towards a small, unremarkable house. "We interviewed them all, of course, but no one saw or heard anything. We've told them that there's a dangerous gas leak, and they've been given compensation." Her radio crackled.

"Sergeant Jenkins to Captain Stewart, over."

"Hang on a moment," said Stewart to Aaron, unhooking the radio from her belt. "This is Captain Stewart. Over."

"Captain, we have a . . . we have a situation here at the crime scene. Over."

"Explain, Sergeant. Over," said Stewart, coming to halt and holding up a hand for her visiting FBI agents to do the same.

"We have a Code Nine."

Complete and utter shock flashed across Stewart's face, and she nearly fumbled the radio.

"Over," Sergeant Jenkins (who sounded young and somewhat shaken) added belatedly.

"Did I here you correctly, Jenkins?" asked Stewart, quickly regaining her composure. "A Code Nine? Here?"

"Yes, Ma'am. Right here in front of me," replied Jenkins, taking his superior's lead and dropping the stiffly formal wording.

"Alright. I'll be right there," said Stewart, beginning to walk again with a new urgency.

"What does Code Nine mean?" questioned Hotch as he lengthened his stride to keep up.

"It means that the Doctor is here," said Stewart. She said the title like a name, and traces of excitement and fear showed through her professional mask.

"Who's the Doctor?" asked Morgan.

"If the stories hold true, then he's the smartest, bravest, best man you'll ever meet – and also the most dangerous."

They had reached the house. Stewart led them through the wide-open front door and into the kitchen, where a young man – presumably Sergeant Jenkins – hovered nervously, shifting his weight from foot to foot. He snapped to attention as Stewart passed.

"At ease, Sergeant," she said almost absently, not slowing down. She came to a halt as she stepped around the counter, and Aaron had to step to the side to see.

The first thing he noticed was the body. It was shaped like a human, to some extent, but clearly was not. The green scales which covered every visible inch of it made that obvious, not to mention the vicious looking claws and slit-like pupils in its yellow eyes. The face bore some resemblance to a crocodile's snout, but it was muted and softened, and no one could mistake the look of terror on the alien's face.

The second thing he noticed was the man crouched beside the body. He was wearing a brown, pinstriped suit under a long, tan trench coat, with incongruously casual converse. From this angle, most of his face was obscured by his artfully mussed brown hair. It took him a moment to register their presence, during which time he muttered to himself in a British accent – London, if Aaron was correct.

". . . but who would have that kind of knowledge? Well, Torchwood, maybe, but they don't go about assassinating peaceable aliens – well, not anymore, anyway – oh, hello!"

He sprung to his feet, grinning. His smile was wide and toothy and blinding, his movements bouncy and energetic. It was very, very distracting – intentionally so. His manner was perfectly calculated to draw attention away from the sharp glint in his dark eyes. Smart and dangerous, Stewart had said. Aaron believed it.

"Doctor," Stewart greeted briskly, snapping to attention and saluting.

"Oh, don't salute!" said the Doctor, cringing exaggeratedly – but while his dismay was overstated, it wasn't entirely manufactured. Interesting.

"Sorry, sir – Doctor," she modified, as he winced again. "I'm Captain Stewart, I'm in charge of this investigation. These are Agents Aaron Hotchner and Derek Morgan."

"Ah, yes, lovely to meet you," said the Doctor, shaking their hands with a firm and ice-cold grip. Despite his polite words, his smile became somewhat fixed and there was a touch of frost in his eyes as his gaze flickered to the guns on their belts.

"They're from the FBI's Behavioral Analysis Unit," Stewart elaborated.

"You're psychologists!" exclaimed the Doctor, his eyes thawing and his grin turning more genuine. "Oh, that's just brilliant," he continued. There was something slightly condescending in his delight. It was the same sort of tone that one might use when praising a particularly clever dog. "I love psychologists. Well, most psychologists. Well, I say 'most' . . ."

"Have you been briefed, Doctor?" asked Stewart, regaining the Doctor's wandering attention.

"Ah, yes, Leroy here was just explaining," said the Doctor, rocking back on his heels and nodding at Sergeant Jenkins, who looked more than a little terrified at being pointed out. "He hadn't quite gotten to the specifics, though. This would be . . .?"

He gestured to the body, reminding everyone of why they were there. Jenkins handed Stewart a file, and she began to explain to both the Doctor and the FBI agents, speaking over the sharp buzz of some device which the Doctor was running over the body.

"We called him Edward White; his birth name was . . . he wrote it down for us –"

The Doctor sprung to his feet, snatched the file from her hands, glanced at it, handed it back to her, and crouched down again, all in the space of about two seconds.

"It's pronounced" (He said something which involved several sharp clicks and sounded physically painful.) "No wonder he looks familiar," he commented, almost to himself. His manic energy had drained away, the darkness of his eyes spreading over his face and making him look very, very old.

"You knew him?" Aaron asked, a suspicion which had been tugging at the edges of his mind suddenly growing much more insistent.

"Well, in a way," said the Doctor with a sniff, recovering his bounce as he leaned back. "He arrested me once. Long time ago. He was just a kid, then. From" (He made another impossible sound.) "wasn't he? No, sorry, you'd call it Capella V."

"Um, yes," said Stewart, consulting the file. "He was one of the first individuals in our relocation program. He came here in the early eighties as a refugee when there was a revolution on his planet."

"I started that, I'm afraid," said the Doctor with a grimace. "It's a pity, really. He had potential – helped us escape. Well, Jack said that he did. Personally, I'm don't think that letting Jack nick the keys off his belt while snogging the life out of him is quite the same thing – having the captain's tongue down your throat can be very distracting." The Doctor seemed to realize what he had just said, and cleared his throat uncomfortably. "Not that I'd know, of course."

"Of course," agreed Stewart, very carefully not amused. "I should inform headquarters of your arrival. The three of you feel free to look around; Jenkins will answer any questions you have. I'll be back a few minutes. Doctor. Agents."

She gave a sharp nod to each of them and departed.

The Doctor turned his attention back to the body. Aaron exchanged a glance with Morgan, who raised his eyebrow in an expression which clearly said what the hell just happened? Aaron shook his head in reply.

"It's a crime scene. Treat it like one."

"Alright," said Morgan, and looked around, obviously struggling to fall back into familiar though-processes in such an unfamiliar situation. Aaron didn't miss the way the Doctor's posture shifted, or how his eyes tracked Morgan's movements with interest.

"The unsub came in through the back door," said Morgan, pacing over to the door and examining the lock. "Looks like he picked the lock without much trouble, so he's got some experience with breaking and entering. Probably has a criminal record." He moved over to the body, crouched down opposite the Doctor. "Do you mind?"

"Oh, by all means," said the Doctor, standing and stepping away with a sweeping wave.

"Puncture wound in the side of the neck, just like the others. This one's on the left, though, so assuming the unsub's right-handed that'd mean he was facing his killer. It looks like he saw what was coming."

"But none of the neighbors heard anything," said Aaron. "He was obviously frightened, so why didn't he scream?"

"Ah, I can answer that one," the Doctor interjected. "This species isn't capable of screaming. Haven't got the vocal chords for it. He wouldn't have been able to make a sound loud enough for the neighbors to hear, even he had the instinct to try."

"Right, Doctor . . . what was it?"

Morgan drew himself up as he spoke, his stance turning subtly confrontational. Classic alpha-male posturing. All of Aaron's education and experience told him that the Doctor (clearly an alpha personality himself) should have responded in kind. The fact that he didn't solidified Aaron's suspicions.

"Just the Doctor." No straightening of his spine, no instinctual attempts to look bigger – but the Doctor's grin went brittle and his eyes darkened in a way that Aaron wasn't entirely sure was figurative. Posturing of a different sort. Not all power was physical.

"So you're an alien expert?"

"More than that," said Aaron, by now quite certain. Cold skin, odd clothing, almost-not-quite normal reactions . . . and UNIT had a special code for his presence, for god's sake. "He is an alien."

"What?" demanded Morgan, looking completely thrown.

"I am, actually, yeah," said the Doctor. He tried to sound casual, but Aaron could see him suppressing a flinch as Morgan recoiled. "Is that a problem?"

"Of course not," said Aaron, ignoring the incredulous look Morgan tossed him. Though their personnel were wary of him, UNIT obviously trusted the Doctor – indeed, Jenkins was quick to jump to his defense.

"The Doctor is a great ally of Earth, sir," said the young sergeant.

"Yes, exactly, thank you. Now, if we could get back to the matter at hand?"

"Yes, let's," agreed Stewart as she reentered the room. "What do you think of it, Doctor?"

"Well, the killer is definitely human, or at least very good at pretending he is. Picking locks, using needles for injection – any alien with the technology for interstellar flight would have more advanced tools."

"But?" Aaron prompted, feeling the weight in the Doctor's dramatic pause. The man certainly liked to put on a show.

"Buuuut," said the Doctor, drawing out the word, "he's not working alone. I can't get any reading at all on the poison he used, which means that whatever it is, it's either completely untraceable or metabolized almost instantly. That sort of thing, especially for a reptilian species, is way beyond human engineering capabilities in this century. There are only two people I know of with the knowledge to create something like that here and now, and one of them is in Cardiff. At least, I think he's in Cardiff."

His eyes went slightly unfocused for a moment, as if he was listening to something far away.

"Yep, definitely in Cardiff," he concluded with a nod.

"And who's the other?" asked Morgan.

"Me. And I wouldn't need to pick the lock; or use a needle."

The Doctor's tone was light, but there was no mistaking the expression in his eyes as he met Morgan's. It wasn't a challenge or even a threat so much as it was a warning.

I am not soft; I am not safe. Dislike me all you want, but do not get in my way.

For the first time since Aaron had met him, Morgan blinked first.