Which finds him in a room heavily decorated in Halloween kitsch, with a pair of highly startled teenage girls, one of whom drops the piece of chalk she was using to draw a highly ornate mostly-circular design on the floor.

Cam looks around. "Didn't anybody ever tell you not to draw on the floor?"

"No! Nobody told me that. I don't see how random floor doodles constitute an invitation to random teleporters anyway."

"...Didn't anybody ever tell you anything? I'm a demon. You summoned a demon."

"I get told lots of things. More than you, apparently, what abusive hyper-religious family decided to tell you that a tail and wings made you a demon?"

"...Excuse me? It's a purely technical term. It'd apply even if I didn't have them."

"Technical term for what?"

Cam sighs. "Okay, Daeva 101. There are three kinds! Angels change, fairies move, demons make. If you draw on the floor in the right, or in this case wrong, way, one may appear! Daeva are passing acquainted with economics and the ones who show up to summons are interested in engaging in trade with you! As a general but not absolute rule demons are the ones with bat wings, fairies are the ones with bug wings, and angels are the ones with bird wings, but if you get a jokester you might find angels and demons with any kind or any of the three with no wings at all. Other cosmetic features vary, although I will have you know my tail is very fashionable. Also, drawing on the floor when you don't know what you're doing is insanely dangerous and if I were so inclined I could already have destroyed this planet, so, you know, don't do it any more, but I'm a nice demon and as long as I'm here do you need any stuff made?"

"My dad could probably destroy the planet if he really put his mind to it. I've never heard of a daeva before in my life. Why the hell should I believe you aren't just some random mutant playing pranks? Because if you are, the Xavier Institute was one of the most idiotic places you could possibly have picked for it."

"...My probability that you're Amish and that's why you didn't know what you were talking about has declined."

"I'm Jewish."

"And last I checked Jewish people as a group did not tend to form little communities of people who do not tell their children that daeva exist! I mean, I think the ultra-Orthodox have a lot of rules about summoning us, but that's not the same thing as 'a winged man has appeared in the middle of a circle I drew on the floor, what could possibly be happening'. So, uh, where the hell am I? Or when. Time travel would also explain this. You're speaking English, which is something..."

"The Xavier Institute, Westchester, New York, 1980."

"Time travel! And possibly also alternate universe, if you have an explanation for me that isn't 'I'm a demon'. But you have a New York, so not that alternate. Is there such a thing as Finland, exactly one moon, cheese danishes, etcetera?"

"Etcetera, I would assume so. Are you saying there aren't mutants where you're from?"

"I mean, do you mean polydactyly and trisomies and intersex conditions, or do you mean 'fully functional, snazzy-colored, matching set of wings and a barbed tail', when you say 'mutants'?"

"I don't think I've met anyone with both wings and a tail in particular, but yes, that one."

"Yeah, we don't have those. I could put wings and a tail on a human but by far the most conservative explanation for me back where I'm accustomed to being summoned to is that I'm a demon."

"And being a demon gives you teleportation abilities...no, you said I summoned you by accident."

"Right. I can't teleport. Even fairies can't do that, they can just zoom around real fast."

"I'd probably be more skeptical of your story but you don't really feel like a mutant anyway."

"Feel like one? We are not so thoroughly acquainted."

"I mean your mind isn't shaped like a mutant's. I'm a telepath."

"I'm not reading your mind. I'm just observing that it exists, and I literally couldn't stop doing that barring what amounts to torture."

"Right, well, continue not reading my mind. You are allowed to know that I have one. I am not sure where between these extremes whatever you're doing to determine that I don't 'feel like a mutant' falls, please explain."

"Okay, so the metaphor I usually use is that it's like I'm walking through a library, and without deliberately looking I see the spines of the books, the way they're bound, the title, whether it's a hardcover or paperback. Reading minds is like picking a book up off the shelf and reading it, except that I'm much better at keeping away from specific things in peoples' heads or only looking at certain things than most people are at doing the same with a book. Mutant versus not-a-mutant is roughly a hardcover versus paperback thing."

"And what here stands in for the color of my spine and how many pages I have and so on?"

"English doesn't have words for telepathic aesthetics but everyone has a unique mental signature--if I saw you again in a very good disguise I could still tell it was you, but that doesn't give me information, for the most part, about what 'being you' means. Pages could I guess be roughly analogous to mental horsepower--people whose brains are more active are sort of synaesthetically brighter. Not that I have synaesthesia, mind, it's just that English really doesn't have words for it. And it is mental activity--someone whose brain jumps from subject to subject and can't pay attention may well register the same as a scientific genius."

"I'm flattered. If you're really scared of having your mind read against your will you might want to hang around the Institute for as long as you're here, though; we have a few other telepaths but we all have the same standard of ethics. There are other telepaths in the world who are less scrupulous. And one thing telepaths can do is shielding minds from other telepaths' intrusions."

"Is this a mutants thing? How does a genetic wobble of any magnitude yield telepathy?"

"I mean, telepathy isn't the strangest thing any of us can do; we have teleporters and people who shoot plasma beams and shapeshifters and telekinetics and people who look like telekinetics but actually work some other way and all sorts of things."

"Which is news to me. How does genetics do any of that? I mean, maybe shapeshifting, if they just take really conveniently after their cephalopod distant relations, but..."

"Of the three shapeshifters I'm aware of, two can look like arbitrary other people and the third turns into diamond."

"Two cephalopods and one for the what-the-fuck pile, then."

"Does magnetism fall under 'cephalopod' or 'what-the-fuck'? asks the other teenager, who up until now had been silent.

"What the fuck," says Cam. "I mean, if you do more than sense it. I think birds can sense it, so that's at least loosely biologically conceivable. You can talk! I had wondered."

"Well, I don't always have to. Edie knew what I was thinking about what was going on, and if had turned out you were hostile it might have been helpful to have one of us not attracting your attention."

"So you could magnetize me?"

"So I could restrain you. With metal. Which I would magnetize."

"I see. For future reference, although you should definitely not summon randomly selected unbound daeva ever, ever again, if you two encounter a random unbound daeva that wishes you harm, go directly to psychic warfare."

"Noted. In my defense, we thought you were a teleporter. In fact, both of the other teleporters of our acquaintance look like demons too, so that supported the theory."

"Could a teleporter not get out of a metal cage or whatever, in your experience?"

"In my experience a teleporter who made a grab for my best friend who teleported out of restraints would no longer be inches from grabbing my best friend. And if they continued attempting to grab either of us restraints would quickly drop off the menu."

"Ah."

"I'd rather not hurt anyone, but I'd more rather not get kidnapped."

"Naturally."

"So you said you can make stuff, right? So you're some kind of super-craftsman or matter generator or what?"

"Matter generator. I can't do antimatter, there's pretty sharp limits to how much information processing and handling I can embed in an instance of making, and I have a range limit measured in astronomical units but can most precisely place things given precise maps or line of sight. Also where I'm from it's the year 2159 and I have thorough educations in medicine and engineering and hobbyist-level computer science. I'm a useful person to have around."

"You know what you should do, you should talk to Dr. McCoy."

"Should I? By all means then."

"He is our science person! He invented a bevy of helpful machines and has done some worthwhile medical stuff although after the incident where he turned himself blue and furry someone else always checks his notes on the latter."

"It sounds like I should talk to Dr. McCoy. If he prefers not to be blue and furry for any reason, possibly also an angel should talk to Dr. McCoy, but only after we know more about how this unexpected universe interacts with daeva summoning."

"I do not deal in souls."

"Okay, the lab's this way," she says, opening the door of the room and gesturing for him to follow her.

Cam follows.

Cam is given some odd looks by the people they pass in the hall, who are mostly teenagers or younger, but this seems to have less to do with his wings and tail and more to do with his lack of shirt. The person with wings he sees, who briefly interrupts their progress to discuss some kind of social thing with his guide, is wearing a shirt, tailored to fit around the wings.

Well, if anyone asks Cam to put a shirt on, he can do that. He doesn't feel inclined to put one on just because.

In they go to meet Dr. Blue And Furry?

"That's me! What are you a doctor of?"

A bunch of things, apparently.

"Cool. I have what amounts to several technical qualifications, but they're from the future - albeit not a future with the local kind of mutants - and backed up with magic. Are you a good place to dump lots of advanced medical knowledge and feel confident it will be distributed generously?"

"I can't say I'm the best possible person to distribute it, but talking to me is almost certainly more efficient than trying to convince someone else to believe you."

"I mean," says Cam, "I can prove the magic part. And the technology part. If you know who else I should ideally be talking to I can go talk to them after making them future gadgets from thin air."

"It's not only your capabilities you'd have to prove if you went to, say, the government, but your benevolence, and in my experience that's a fair bit harder. I can get these things distributed, it will just take a bit longer."

"Yeah, fair point. Malaria I can fix myself in a day trip, everything else ought to have a non-daeva-based pipeline from synthesis to prescription. Lemme start you with some books." Cam makes him a stack of books.

"How on earth do you intend to fix malaria in a day trip?"

"Oh, I mean it will still exist after the day trip. The active work will just be done then. An overwhelming population of sterile male mosquitoes will do the rest."

"Aha. Clever of you."

"I can't claim credit for the idea."

"Oh?"

"It was implemented on the Earth I'm more previously familiar with. Nobody consulted me on the project."

"Ah. Well, it's good of you to replicate it in our universe, as it seems to be. Was the rest just these books, or was there anything else?"

"Oh, there's lots, but it seems more efficient to start you on the books while I'm off making mosquitoes. Will you be able to read more than that in the next twenty-four hours?"

"Yes."

Cam goes hmmm and makes a futuristic little computer and looks through its display as it shuffles around. "Any chance you read Chinese? I can probably find a translation of these ones but I don't already know one..."

"I do, actually."

"Cool, so I can throw in these - I'm reasonably sure you don't know Lagalann, that's a demon language - Latin?" More books appear.

"Yes, actually. To the Latin, you're quite correct that I don't speak the demon language."

Some Latin books join the pile. "Okay, so, these are my demon medicine books, most of them from 2039 to start you off with relatively more context, and this stack is an update on the series from more recently. Because they are aimed at demons they say things like 'apply an even distribution of a total of 2ccs of metracorazone to the arterial blood' or 'if you are permitted to speak and working with other daeva, ask attending medical fairy to suppress blood flow to the tumor' as opposed to things like 'inject this stuff' or anything else demons easily work around. However, they do have chemical formulae even though we don't strictly need them so that we can make judgment calls about unexpected possible drug interactions, and conversion tables and sidebars for talking to human doctors, so if you're six-PhDs-and-multiple-languages smart you should be able to work backwards and get a lot out of them. Do note any questions you have for me and I'll be able to clarify out of my notes when I come back. Sound good?"

He is already paging through the books. "Sounds great."

"Awesome. It is a little early for you guys to have a functioning Internet, so do you happen to know off the top of your head what regions of Earth are currently affected by the malarial mosquito?"

He reluctantly abandons the shiny new books to look through some periodicals, and names some places.

"Great. And can any of you point me to a good place to take off in a sedan-sized stealthy spaceship?"

"Somewhere on the lawn that doesn't have anyone there should be fine."

By this time, Dr. McCoy has finished the books Cam gave him, and someone has informed the Professor of all this business.

Well, Cam doesn't know that there even is a Professor except insofar as the man with six PhDs may qualify, so he goes looking for Dr. McCoy to fill in any gaps the stack of books left.

He appears to be talking to a man in a wheelchair.

Cam can wait.

They break off a few moments after Cam gets there, and the other man turns to face him. "Hello," he says. "You must be...the demon. Whose name it would appear my daughter and her friend neglected to ask for. I'm Professor Charles Xavier, and I run this school."

"My name's Cam. Hi again, Dr. McCoy, did you like the books?"

Dr. McCoy begins expounding enthusiastically on the contents of the books.

On which Cam will happily converse.

The Professor will wait for an appropriate lull in the conversation, but eventually he asks, "Not that I don't appreciate the advance of medical technology, because I do, but I'm a bit concerned as to whether there are likely to be any direct consequences, negative or otherwise, to one of my students having summoned a demon."

"Well, I can't say for sure, but apart from the obvious presence of said demon it's possible that when she dies she'll become a daeva. I have never heard of anyone turning up in any of the daeva realms claiming to have come from nearly two centuries earlier in a world with mutants, so it's probably never happened that way before, but perhaps this is literally the first time anyone here has managed a summons in the first place."

The Professor flinches slightly, raising a hand to rub his temple. "She seems particularly distressed by this prospect. Is there any way of reversing it?"

"No. But it might not take effect at all; like I said, nobody from this world has ever seemed to appear in mine that I know of. And if by some well-kept-secret people here are attached to my set of postmortem options, being a daeva is much better than the alternative."

"She's distressed by the possibility of being separated from her loved ones, apparently." He doesn't look unsympathetic to the concept.

"Well, if I can be dismissed and resummoned normally other people can also summon me and share it around. Although there's also no way to guarantee that they'd all be the same kind of daeva, and visitation opportunities are few."

"She's also distressed by the possibility of denying her father the opportunity to see his mother again, if our universe has a native afterlife. She seems to be seeing it as being stuck between a rock and a hard place."

"I'm really very sorry about that, but I'm sincerely unaware of a workaround even if we assume everything I know about my world applies here, and I think you understand that I couldn't reasonably warn her in advance."

"I understand. But that one, I can't fix."

"I don't object. Although in case I can't come back, do you suppose she'd mind waiting until I have a chance to terraform Mars? I've always wanted to terraform Mars."

"I imagine she'll be willing to wait."

"Cool. I will hang out here, chat with Dr. McCoy about medicine and give him more books, and then fly to Mars, if there is no objection."

"No, none."

Edie is waiting when he gets back.

"Hi. Unless Dr. McCoy has more medical questions you can get rid of me now."

"And how do I do that? And how does Emily summon you again?"

Cam hands her a piece of paper. "Summoning instructions. Don't deviate from them. You get rid of me by concentrating for about a minute. I really am sorry about the surprise potential afterlife complication."

"...If your world is wholesale hooked up to my world's afterlives, your grandma will be in Limbo, and you will be able to send and receive mail wherever you wind up."

And eventually no more demon.

And Emily draws the circle to resummon him.

"Hello. Well, it looks like summoning works more-or-less as normal in this universe."

"Seems like it. Which is good to know if, say, Professor Xavier wants to get out of his wheelchair, or if any locations need to be deradiated, or if you want to run an electrical generator on books and candy and interesting shoes."

"I don't think either of us are going to claim the third option appeals. But--the first one, that."

"Cool. I can recommend you a medical angel and do most of the circle for you so you don't have to worry about getting a binding wrong, even."

"Well, I should actually ask him first. I strongly predict the answer will be yes but that doesn't make it okay to make arrangements for his medical care without consulting him."

"I cannot bring a medical angel to this world without assistance. Daeva cannot perform summons."

"I'm not an angel. But at a guess she'll ask what the nature of the problem is, if it's particularly complicated she'll anesthetize him and open him up to have a look at it, and then she'll change whatever he's got into functional whatever-isn't-functioning. Won't even leave a scar."

"He was shot in the spine almost eighteen years ago."

"Probably take a decent medical angel five, ten minutes. Longer if he wants her to fix atrophied muscles below the waist."

She worries at her lower lip a little, sounding like she's listening to something no one else can hear. "Okay. He says go for it. So: all but last bit of a properly-bound angel summoning circle?"

Cam hands her a rolled-up piece of paper. "You must also be careful about task negotiation. If you are the least bit unsure about that I can do it for you and you can just say 'yes' when I cue you. I mostly trust this angel, but mostly is not absolutely and angels are only a little less scary than demons."

"Noted. Is task negotiation very difficult?"

"It can be. Again, I mostly trust this angel, but I don't want you picking up bad habits - I mean, apart from summoning me personally unbound, but you already knew that was safe."

"I mean, how in particular is it tricky, do I not just tell them what I want them to do and ask them what they want for it?"

"You do that, but if you are imprecise, then there will be loopholes. I can teach you summoning properly if you like, but if you don't want four college credits of it before the professor gets to walk, let me do this one."

"I don't think it came up."

"I accept."

The angel picks up the orange and steps out of the circle. "Where is my patient?"

Edie goes a little green, but says, "I will."

The angel wants Xavier face down on a table. She has Cam anesthetize him from the wound down, which Cam does. Skin parts under her scrutiny; she investigates the spinal damage. She connects things up. The skin knits bloodlessly together again. "Do you also wish your leg muscles restored to active condition?" she inquires of the patient.

"...Yes."

So she does that. She doesn't have to open anything up and look at it for that. When she's done, the feeling in the professor's legs abruptly comes back.