"I'm not trolling... and you knew that... and you said it to see if I would call you out on that."

"Correct.  Though it's not so much the binary choice of whether to contradict me, as all the side-channel information, like how long it takes you to decide and how your breathing changes."

"What is the average wing speed of a swallow?"

"Hold on, let me think about that one..."

"I ask that you reason out loud, to the extent you can."

Meanwhile and in another room.

"Got a baseline.  Thanks."

"So.  What, on your own best guess, happened today?  Not just on the plane, but the larger context."

"Wow.  I was sure that was just a fictional trope in detective stories, intended to let the audience make their own guesses and maybe bet in some prediction markets before the story ended.  I did not expect it to be a thing in real life."

"It's in fact a difficult problem to present a criminal mastermind, that they have to accurately guess how much all the innocents will guess; and if they fail to 'guess' what everyone else saw, or 'guess' a fact nobody else guessed, it stands out.  But you need a Keeper to read side-channel information or it's not really worth it, and it also works noticeably better when you've got a larger population to use as a baseline.  So it's done on a few serious cases, too serious for a criminal mastermind to train themselves on that part of the procedure by making themselves a suspect in something more innocent in order to observe law enforcement response afterwards.  Obviously, we ask you not to be too loud, afterwards, about what exactly happened during this part."

"If you manage to get things right that nobody else on the plane got right, we'll present you with a Keeper Certificate of Having Done Something Impressive You Can't Talk About accordingly."

"Not actually likely to be an issue."

"So.  Um.  What do I think happened... sorry, it's going to take a second to pry my brain loose from imagining my readers gathering in an online forum to argue about that while the story's online publication pauses for an hour."

"Take your time.  But also, think out loud while taking your time.  This isn't really a test of your reasoning abilities; it's a trap you're helping to establish a baseline for."

"Right, so."

"In real life, I think it was supercriminals, mainly because the onboard prediction market said it was supercriminals and it's hard to think past that.  Showing up with a lot of Keepers is making my brain suspicious that they were not entirely mundane criminals, but that is probably just story logic talking and there's also the Supervisors of Economic Conduct which is less likely if Aliens Did It.  I would not even usually be saying all this out loud in a Very Serious context, but you asked me to think out loud."

"What was the criminal motive?"

"Not just betting about the plane, I don't think, because that would just be rolled back.  Even trading on the airline, the plane manufacturer, or the insurer, seems like it could be mostly rolled back, and like there'd be only a few suspects for trades that diverted and ended up impossible to untangle.  Also, one of the last pieces of news we got from the cockpit was that Exception Handling thought our plane had not totally lost comms, which would have reduced market interest and liquidity by a lot, with few distracting-participants to present a crowd for the real criminal to lose themselves in... or mostly, there wouldn't have been much market movement at all, if our plane didn't vanish."

"So it wasn't about trading on direct alarm presented by a lost plane.  They didn't maximize that alarm, they minimized it, maybe so we wouldn't get the Exception Handling supersonic escort we were expecting to show up.  The part where that made us look like we'd been isekaied was a distractor."

"The main thing they wanted... was for our plane to not be in communication with Civilization, and for the rest of Civilization to not think this was all that suspicious."

"I am not instantly seeing where to take it from there... I can go on trying to talk faster than I can really think... a CEO on board our flight, and somebody steering a company to make a really bad decision that the CEO would have overruled if they'd been in contact.  The isekai thing could be about some sort of personal connection with that CEO, wanting to prank them personally.  Doesn't really fit, it feels like it'd be too obvious afterward what'd happened, and who'd done it.  There ought to be easier ways to take a CEO out of contact while their company makes a stupid decision."

"Okay, that was my brain's first stupid idea, if you want a second stupid idea it's not coming as easily but I can go on thinking."

(In another room.)

"What happened?"

"Supercriminals."

"Why?"

"I think the point at which I felt sure was when they told us that our short-range radio to Air Traffic Control had worked.  That's uniquely predicted by criminal masterminds.  There's no physical phenomenon that messes with all the radios except the ones you need to land.  That's the work of a mind that wants to mess with your comms for a few hours, but doesn't see a point in messing with your comms for an additional ten minutes at the price of maybe causing your plane to actually crash."

"Why supercriminals, plural?"

"Bit of work for just one person, especially taking into account whatever they had to do on the other end of this to take advantage."

"You don't think it was a prank to make you believe you'd been isekaied?"

"Maybe I was just Kelthamomorphizing the rest of Civilization, in my reasoning, there.  But I didn't believe in pranksters that determined to altruistically provide the rest of us with a fun life experience, at that price."

"Somebody planned to make a very large profit.  I believed that even before the SEC showed up in power armor."

"Why try to fake the rest of Civilization having fallen silent, like there was no one out there?"

"I don't think I would have done that part if I were a supercriminal.  In some sense, that part does need to be a prank, unless I'm missing something, because the way we felt on the plane had no way of influencing the rest of Civilization where the events were happening that the criminal planned to actually profit from."

"My guess is they had to do most of the work that would need to be involved, for other reasons, and then they saw the chance to pull a full-scale isekai prank, and took it.  And the partner who fell in love with this idea, sold it to their other criminal partner by arguing that, if the people on plane deduced exactly what was happening and had no distractors to make them want to put aside the whole confusion to focus on safety, they might pierce the plan."

"There were things we could have done to try to signal Civilization, like drilling a wire through to try to use the airplane's exterior shell as an antenna.  We'd have been more likely to do those things, if we'd been sure that our comms had been cut by adversaries, and that there was a supercriminal plan to make a massive profit, and that this plan had a key turning point which was to cut our plane's comms with Civilization."

"At least, that's what one criminal partner said to the other one, and then they promised to do all the marginal extra work themselves for faking the isekai scenario, and their criminal partner sighed and let them get away with it.  Call it a 3:2 likelihood ratio that they were romantic partners and not just criminal partners, this is exactly the sort of thing that one partner lets another partner get away with because their birthday is coming up."

"That's a lot of helpful detail you're coming up with very quickly," the Keeper does not say, because Keltham was explicitly asked to do that in order to make life harder for supercriminals who need to come up with plausible details quickly and not correct details and also not details that sound too obviously incorrect while a Keeper watches them breathe.

"This entire event is occurring on the mastermind's birthday!"

"No, actually, I take that back, that would be too much of a giveaway against serious info-theoretic opponents and they are absolutely facing those, they have Keepers after them."