Then he'll probably hear the voice before he sees its owner, as a little gaggle of socialites wanders in his direction. It's a voice he might recognize, attached to a familiar face.

Not because they've encountered each other at one of these things, of course -- he'll have seen the interviews, most likely. (Mr. Wayne, will you be taking over from the board of directors? Mr. Wayne, how are you planning to juggle Wayne Enterprises with your higher education? Mr. Wayne, how does it feel to be voted Gotham's most eligible bachelor this year? Mr. Wayne, everyone's wondering just what you've been up to abroad...)

Apparently some of what he's been up to abroad is getting into cultural misunderstandings with a woman he met in Delhi! He's having a great time telling his little audience about his mishaps. They seem thoroughly charmed. None of them seem to have quite noticed him yet, except for possibly Bruce himself, who glances briefly in his direction before pushing forward with gusto to the punchline of his current anecdote. His friends laugh.

The Jolly Ranchers are shucked with even greater attention. 

Bruce's anecdotes reach a natural stopping point; his listeners turn more towards each other, and he wanders off to the next conversation.

The nearest unoccupied person, as it happens, is Lex.

"Those any good?" he asks, still casually cheerful, nodding vaguely at the Jolly Ranchers. (He's having to angle himself a little awkwardly to avoid cornering him or ending up with his back to the rest of the party. Possibly this is by design.)

Lex's fingers continue to tap; his legs start to jiggle.

"Mm. Do you know about the chicks of herring gulls?" he remarks. "Some, ah, particularly cruel scientist painted a knitting needle red with three white circles. The chicks begged far more enthusiastically from that than from their parents. Truly a shocking lack of filial piety."

"I'll stick to the watercress, then," he says, his bright smile faltering slightly into something more nervous and intense.

"Aa aa aaa," Lex says, "my good sir, man reshapes all that he touches. The cress in your sandwich is as far from its original plant as a dog is from the animals which stalked the Neanderthals at night when the fire went out."

"I mean, we of all people can't object to that," he says, regaining some of his mood. "I'd have to close at least three branches of the company if I decided I didn't like my plants engineered."

"The conquest of nature," Lex says, "is the development of better and better superstimuli. I hold the progress of humanity in my hand, small and full of, mm, high fructose corn syrup." Crunch. 

"Maybe I will have one then. If you don't mind?" He's not exactly joking and he's not exactly laughing at him but he does seem to be internally laughing at something -- himself or the situation or some private joke.

Luthor gives him a Jolly Rancher.

"Careful not to lose your cruel body, Tom Buchanan, lest you drift on forever seeking, a little wistfully, for the dramatic turbulence of some irrecoverable football game."

"I shall make sure to fast for a week." He pops it into his mouth with great solemnity.

"Surely there is someone less awkward and incomprehensible you could talk to."

"Nobody else here brought their own superstimulus, though," he says, pushing said superstimulus into his cheek to respond. "I suppose I could go find Julie Madison again, now that we've reacquainted ourselves."

"Julie Madison brings her own superstimulus with her wherever she goes. She's showing it off to, mm, excellent effect."

The tapping is faster and more frantic.

"She is one of the prettiest attendees, I'll admit."

"Humans are one of the few species in which the female adorns herself. If we were bowerbirds you would be the one with the boob job."

"That'd be a bit like us surgically adding horns to our heads, wouldn't it? Surely if we were bowerbirds I'd be focused on artificially increasing the brightness of my feathers."

"Aaa aaa aaa, bowerbirds are drab. The male builds a bower and decorates it. Shells. Leaves. Flowers. Coins. Bullets."

"You don't think they would go for feather dye, if they could use it? And bower-building didn't fit the metaphor as well." --He notices that he's been slowly slipping out of character and subtly corrects, raising his hands in a mildly self-deprecating manner. "In any case, you could hardly accuse me of not filling my home with pretty trinkets to impress the ladies."

"Well, well, well. Percy Blakeney. But I don't see a guillotine."

He smiles; it's unclear whether it's meant to be conspiratorial or condescending or just deeply tired. "You caught me. I was once a little boy who used to play at being doctor in the outbuilding off the back garden. But if you think the man I've become is just a smokescreen for an awkward bookish child, that he'll somehow reappear if you just strip enough away, I'm sorry to disappoint -- I stopped being a child over a decade ago."

"Strange for Jay Gatsby to pretend to be Tom Buchanan exactly," Lex says. "Strange for a man of your wealth to be Jay Gatsby at all. We're, mm, too careless for it. Or perhaps I shall find a card with a small red flower when you take over my company."

"I am still ambitious, I'll grant you that," he says wryly.

"Your bower is the most extraordinarily well-decorated."

"A man's got to do something with his life." He's made it all the way back to safe territory again, back to being gregarious and cheerful and a little bit ridiculous (though somewhat subdued now, which is natural, considering). "You should come see the Kusama I had brought back sometime, it gives the sun room a distinctly modern flair."

"Happy to skip the party to inspect your bower and be, mm, the most impressed of the bowerbirds."

"I think Julie might object," Bruce says, raising an eyebrow. "To both our disappearance and to you in particular."

"I'm very objectionable."

"I wouldn't want her to worry."

"Wise of you."

He stands up and starts walking away.

Introductions and small talk(?) achieved, Bruce wanders off again, to the next rich socialites he really ought to actually meet.

A few days later--

Barry Allen is having a good day. 

He has a few dozen deliveries to make across Central City off various gig economy apps. He has a couple of TaskRabbit tasks from people who don't expect to actually watch him do it; he assembles furniture, cleans a house, fetches someone's dry cleaning, and fixes a toilet. And about ten minutes after he begins work, he's done for the day and can go back to his apartment and read comics. 

If he's still in super-speed mode when night falls, he'll get a few dozen more chances than most people to look up and notice there's something amiss. An open window he didn't open. Shadows falling oddly, shifting when they shouldn't. It takes a relative eternity to cross this room; if at any point he were to just turn around, he might catch his intruder mid-skulk.

Instead, of course, he's going to have a mild heart attack.

"You stopped that robbery," says a voice behind him, deep and raspy and inhuman. It waits until he's finished the issue he's on to say this. It's a considerate nightmare voice.

When you're sped up, it's hard to understand human speech, but the deep raspy nightmare voice is not less startling for that. He accidentally speeds up to country-crossing speed and then slows down to normal human and catches all of the horrible nightmare voice's sentence.

"Why the fuck are you in my house?"

(Barry talks fast, even when he's not sped up.)