Bella slips into the school by a side door; she just saw a thing and she thinks she's seen it in a book before and thinks it's supposed to be mostly harmless but before she wakes Giles up over probably nothing or kills a likely neutral demon she wants to check.
And she pushes into the library.
"Okay, listen," he says. "I have no idea what the hell is going on here. I've been in this reality for maybe four days and I spent three of them unconscious. But you're threatening my friend, and I find that personally offensive, and I am politely asking you to stop."
In slightly better light and with his lower body no longer obscured by the table, it's more obvious that the grey-and-white pants paired with his black T-shirt belong to some kind of uniform. The overall impression is distinctly military, although of a somewhat futuristic bent, and to complete the picture he has a holster at each hip containing two slightly different futuristic weapons.
"Bella the Vampire Slayer, and I'm sure I'd be charmed if I thought I wanted you to have guns but I don't think I want that."
"That puts us at something of an impasse, then, because I don't think I want to give them up while you're waving that thing around," he says, nodding to the crossbow. "Look - whatever you imagine our fundamental conflict to be, surely it won't get worse if you take the time to explain it to me?"
"Depends on what your friend is up to, and it sounds like that might be 'summoning mercenary demon vampires' or something. Look, are you aware that most things that are not human and find themselves in human civilization qualify as serial killers around the third time they get hungry?"
"Well, they do, so I kill them. You are an unusually talkative mercenary demon vampire or whatever you are so I haven't shot you yet but you do not have the default high ground here."
"I'm glad you met a frustrating human and not a delicious one, tell you that. You wanna tell me what you are, put the holstered guns out of arm's reach, and convince me you are not a public menace who won't even leave a body except for the Dustbuster?"
"No! I don't!" he exclaims. "Because you've been pretty clear about the fact that you might try to kill me at any moment in response to an evaluation whose criteria I don't fully understand, and that's not the kind of situation in which I feel it is safe to unilaterally disarm! And the worst part is, four days ago I would absolutely have had that confidence! God I hate this so much!"
"I'm sorry," the voice from the stacks says plaintively, and then immediately freezes still and silent and breathless again.
"So here's what I'm putting together," Bella the Vampire Slayer says. "You are some kind of demon-or-something from another dimension, which is why you are stunningly ignorant of supernatural staples; your friend back there apparently turned you, which means you were at least loosely human to start, although I can't rule out 'extradimensional human population raised as cultist sacrifices to insert Old God here' or something fucked up like that; and now you have broken into a library to correct your admittedly woeful education and think this is the correct situation in which to insist on some sort of respectful rules-of-engagement rigmarole that made sense in your original world while the Slayer has a crossbow and you are ash waiting to happen. That about right?"
"Will you stop flippantly threatening to kill me," he says in a tight voice, "please."
"So how's my guessing?"
"You're missing a few important details," he says. "From my perspective, it looks like this. Four days ago, it was the year 2997 ECE, humans were the only sapient species in the fairly widely colonized galaxy, and I was on my way out of the star system where I'd just successfully rescued a shipload of hostages from space pirates. I had a broken shoulder and a shattered hand from the fight. Then I woke up in an alley not far from here, looking up at Earth's extremely recognizable moon, and it was inexplicably 2005 and there were inexplicably vampires. My shy friend was the first person who found me, and he recommended vampirism as a cure for my injuries, which would otherwise have cost me the hand given the state of local medicine. I accepted the offer as described. And then it turned out I should've inquired more closely about the exact function of a soul. Now I'm - suffering a temporary impairment to my moral compass, which I hope to correct as soon as possible. Hence the research."
"I am a very eloquent person and I truly cannot adequately describe just how utterly insufferable this state of being is," he says.
"I'm an outlier. It's hardly the first time. My fleet surgeon keeps a tally of all the classes of drugs he can't give me because I turn up unheard-of debilitating side effects."
"So you're debilitatingly allergic to the loss of your soul and you came here to research it. You even actually have one of the right books in the pile, well done. Why's your friend here, he want a soul too?"