"The area near the vents got the worst of it." And she leads him to the nearest vent.

Flashlight examines the area near the vents, moving gently and precisely to avoid disturbing the dust, then turns on one of his more conventional-flashlight-shaped gadgets (or that's what his manner suggests he did, but it isn't emitting any visible light) and points it at the dust.

Nothing happens.

He adjusts some controls on the side and eventually the device does show some manner of beam, which makes everything it's aimed at light up with an intense violet glow. He fiddles some more and eventually, after going through a few rainbows, the dust is bright violet and the floor and wall are moderately orange. Stepping back, he pushes a button on the pseudo-flashlight and pulls out another device with a handle like brass knuckles but a lens on the business end.

He fits it onto his hand, points it at some of the dust, twitches a finger on some control, and slowly pulls back. The dust moves with his hand, frozen midair in the shape it was lying on the floor and wall, and the other device shows only orange where it was. Faintly relaxing, he puts the dust back down and says, presumably to some communication device, “Got the dust identified; uploaded the signature. Subtle, but no tricks.”

He pulls a bag with a fitting on one end out of another belt compartment, puts it sideways onto the telekinetic knuckle gadget, and does something to pull the dust down the cone of the beam and neatly into the bag. He uses it to clean the area around and under his feet, then asks her, “With your permission, I'll clean the rest of your apartment?”

...Let's hope that 'bright orange' is the colour carpet is meant to be under... whatever light that was. Presumably it is?

It is kinda weird watching someone Science(!) her living space, and the fact that he seemed slight worried at first is a little alarming, but hey, at least the dust is going away.

"Please, do so. I don't want this hanging around if can be avoided."

(The orange glow is only where he's pointing his gadget. The carpet and wall return to their more familiar beige-or-whatever and off-white when the beam moves on.)

He proceeds through her apartment carefully and thoroughly, moving things aside just enough to collect any dust that might have been under them, and checking with her before actually opening her closet and dresser and such possibly private spaces.

Through the walls she can faintly hear an unfamiliar tone of voice in the neighbor's apartment, and the sound of many footsteps past her door — perhaps everyone else is getting visits too.

She follows him at a polite distance, and gives him permission to rummage as needed.

It's probably for the best her neighbours are getting checked. They might not thank her now, but she can bask in the self righteous glow of helping stop them from breathing eldritch dust.

In half an hour he's finished, double-checked, and tied off the collection bag.

“All done! Thank you for the report and your patience!”

"No worries, and thanks so much for your help."

And gently shuffling him out the door.

Shortly after the door is shut she can overhear what is probably his voice talking to the occupant next door. Besides that, there is still an unusually high background of people-doing-things-or-talking noise.

But she, at least, can put this behind her. What will she do now?

Back to the google. She was thinking about looking up more proactive means of protection, how to stop this from happening again so she didn't have to bring these guys into her apartment again--

But keywords are hard.

And Flashlight used some terms she didn't recognise, that might be useful to know? She searches for "subtle science meaning".

These terms do not appear to have a specialized meaning together beyond the ordinary English ones. A few authors use it in a poetic-language sort of way, and they don't particularly agree with each other.

Huh. Guess it might just be some specialised jargon that hasn't floated out onto the internet then.

She taps her fingers against her cheek.

You know what? She's going to check out the police training manuals (or what non-redacted bits of them exist online.) They seem the least wicky-wacky, and might come in handy in case of future neighborly mad science.

Police training manuals vary a lot! From context, it appears to be mainly due to what kinds of things the local [insert approved euphemism here] get up to and what the particular police force's relationship to available local experts is. When authors have attempted to generalize these, the results are unhelpfully legalistic or wishy-washy.

There is a general tendency to recommend not touching anything (but if you have touched anything, not to panic), and to avoid making assumptions about what some object is or what someone's goal actually is (but understanding borne of repeated practical experience, should you be so unlucky, can be valuable).

Okay, yeah, she probably should've expected any general advice to be less than useful. Not that "don't touch anything, make no assumptions" isn't useful, it's just not a thing she needed to be told.

...what safety advice do mad scientists give other mad scientists (and can she google this without getting on a watchlist)? They're mad scientists, so their safety advice has a good chance of being nonsensical, but if anyone would know the specifics--