Doctor Jessica Scanlon was half expecting the text message. “Lunch?” it read. Short and sweet, unlike her brother.

On the way down to ground level, she resisted the urge to backtrack, to recheck the setup for the next experimental run. To wait, expectant, for the results. They were sure to disappoint, like all the other recent tests. The team would have to rethink, explore yet another section of the periodic table. Stealing an hour for lunch with her layabout brother wasn’t going to change that.

Jess met him by the park entrance, the ribbon of young trees and green lawns that separated the science park from the town proper. A short walk during which she was permitted to talk about her research, before they reached the café and, by mutual consent, the conversation switched to less abstruse topics. Only today, Harry spoke first.

“I got one of those scam aliens yesterday,” he said.

“Really? They’re still doing that?” Jess gave him a sideways look. In the sunshine he looked boyish, carefree. As indeed he was. “I thought they’d have given up by now. You have one unusually cigar-shaped asteroid zipping through the solar system, and suddenly people are getting interstellar cold calls, offering real estate deals on Venus or stock tips from infallible alien supercomputers. I trust you hung up immediately?”

“Well ...”

“Harry! You didn’t?” She stopped, midstep.

“I thought I’d play along for a bit, y’know? Just for fun?”

“Idiot!” She would have punched him on the arm if he hadn’t been a couple of paces ahead. “You know perfectly well what the authorities say. Any snippet of information you give the scammers makes it more likely that you’ll be suckered, if not this time, then the next. Even giving them your name—”

“Sis, I may not have a fancy doctorate like you, but I’m not a complete moron. I didn’t give them my name—”

“Two doctorates, actually ...”

“—I gave them yours.”

Her feet dragged, and her brother halted as well. A dog walker gave them both a wide berth, tutting as she went.

“You what?! Harry, is this your idea of a joke?”

He had the good grace to look at least a little guilty. “Well, technically they already had your name, I just said I was you, is all.”

“Is all? You’d best tell me everything they said.” Only a younger brother could provoke her this way. “Goddamn it, if this comes back to haunt me I’ll have your guts for garters. With the upcoming departmental review and research funding getting cut ... Since when do you do a decent imitation of me?”

“That’s just it, I didn’t. I said I was you, but I didn’t change my voice. That didn’t faze them at all.”

They set off again, at a slower pace. “Of course not,” Jessica scoffed. “They’re reading from a script, right down to the ‘sorry, there’s a delay on the line because we’re in orbit around Mars’ shtick. Any such delay would average around thirteen minutes, but never shorter than four—they can’t even be bothered to lie convincingly. OK Harry, from the top. And don’t you dare skip anything.”

“I don’t know why you’re getting so het up, Jess. I just played along, for giggles? I knew it was aliens as soon as I answered. That distorted voice thing, even before the excuse for the delay. Which is supposedly from Lagrange point 5, whatever that is, apparently a perfect spot to monitor us, with the added benefit that the Cardy-loosky clouds help cloak their presence—”

“Kordylewski?”

“—something like that. In their off-kilter electronic voice, they asked, as polite as you like, if they could speak to Doctor Jessica Scanlon. And I said, in my deepest and most manly voice, i.e. this one, ‘Speaking.’”

Harry’s hands fluttered as he eased into the telling of his tale. Jess thought, not for the first time, that he would have made a good court jester.

“And they replied, yes, they were speaking, and obviously I was speaking, and could they please speak to Doctor Jessica Scanlon? So I said, since they were playing dumb and I was perfectly willing to play dumber, ‘You are speaking to Dr. Jessica Scanlon.’ And they said how wonderful it was to finally get through and they’d been trying for a while, because they wanted to give me—or you, I guess—a solution to a technical issue I was having getting carbon mineralization to lower CO₂ and stop further climate change.”

Jessica blinked. Kordylewski had been enough of a surprise. “That’s awfully close to the truth, Harry.”

“Yes, I guess.” He shrugged. “But it’s not like you keep your research secret, is it? The whole point of a scientific research department is to publish as many papers as possible.”

“And save the planet.”

“And save the planet,” he agreed. “That’s what they kept going on about: saving the planet. Big spiel about tipping points and stochastic mechanisms and the dangers of alternative geoengineered solutions like reflecting solar clouds and other such nonsense.”

Jessica paused for a moment as a jogger ran past, red faced and looking like they were loathing every glorious minute of the unseasonally warm midday run. “I think you mean ‘reflective polar clouds?’ By spraying salt crystals into them, but yes.”

“So not total nonsense, then?”

“Not ... totally.” She didn’t add that one of the other institute departments was close to a prototype, if they could get the funding.

“Parts of it sounded like that paper you asked me to proofread. Using finely powdered tailings from mines as an integrated building material? Yabbering on about carbonate uptake and how the captured CO₂ would remineralize cracks, making concrete heal itself—”

“That paper hasn’t been published yet ...”

“And they said the issues you were having with developing catalysts to increase the absorption rate and engineering suitable nanostructure surfaces would work if you could just ...” Harry trailed off. “Are you OK, sis? You’re looking awfully pale.”

“Yes, yes, I’m fine.” Jessica felt like she always did when a car she was travelling in encountered a dip in the road. A fluttering, organs-in-the-wrong-place sensation. “And they had a solution, did they?” she asked, voice and breath tripping each other up.

“Oh yes!” Harry grinned. “They said it was quite simple, actually, and I’d—you’d—done most of the hard work already, which they were most impressed by, and it gave them hope in the whole human race however many mistakes they—we—keep making. They said I’d—you’d—probably get there yourself in perhaps as little as thirty years? But Earth didn’t have that long, not before the damage was permanent, which was why they were breaking galactic protocol to make this one phone call, and would I—you!—kindly never speak of it to anyone and take all the credit for yourself? Because they couldn’t sit and watch, not when they had the final piece of the scientific puzzle, the key to turning it from theory to practice, which they were giving to us for free.”

“For free?” Jess’s voice sounded distant, like it was coming from the next room. She felt the prickle of the sun on her forehead.

“Yes!” Harry shook his head, rueful. “I was most disappointed. I was waiting for them to ask for my credit card details to prove I was who I said I was, i.e. you. Or to download an app onto my phone or PC to give them remote access so they could ‘send the data.’ Or to transfer a fee to unlock an African prince’s inheritance.”

“That’s the 419 scam.”

“Please, don’t remind me. But this lot didn’t want anything, which caught me on the hop. Instead, they asked if I was ready to write down what they were about to tell me.”

“And ... Harry, were you? Did you? Write it down?” Jess’s hands clenched and released as she stared at her brother, who stared back, eyebrows raised in amusement.

“Of course not, Jess! It’s a scam, yes?”

“But ... oh god. Do you remember what they said? Anything at all?”

“No. I’d put the phone down by then.”

“You put the phone down?”

“I told them we already had one, thank you very much, and hung up.” Harry shrugged again, his contented smile that of a grown man declaring “mischief managed.” “Hey sis, where are you going? I thought we were doing lunch?”

They’d reached the end of the park, a mere fifty yards of bright pavement from the café, and the first of the twin church spires that bookended the shimmering high street. But Jessica had turned back the way they’d come. “I can’t, Harry. I’m heading back to the lab, and I’m afraid I’m going to be too busy for luxuries such as lunch.”

“Too busy? For lunch? Seriously, sis? For how long?” Harry called after her.

“Oh, about the next thirty years by all accounts. Perhaps I’ll see you then, little brother, if the flood waters or the extreme heat or the invasive species don’t get us first.”

She glanced over her shoulder to where Harry stood, adrift, and shook her head. He was too far away to hear her, but she said it anyway. “Though even thirty years might be a lifetime too soon.”