I spot Seth as soon as he walks into The Fellow, even though I’ve never seen him before. I can tell it’s him from his hairstyle and bag. Unlike me, he is visibly creative. He doesn’t spot me, even though only nine months ago he uploaded 20 carefully chosen photographs of me onto the ‘Gallery’ page of my website.

Today I have my hair up because I didn’t have time to wash it, but I don’t think that’s why he hasn’t noticed me. I think it’s the famous/ normal thing that most people can’t handle. If you’re famous – even as a writer, and writers are much less visible and of less interest to the general public than other famous people – there’s a tendency to assume you cannot also be ordinary on any level. People say to you, “What, you’ve got flu? I didn’t think bestselling writers could get flu.”

I wave. Seth does a double-take before blushing and waving back. That’s right: no shiny aura of celebrity, just a woman in a shirt, jeans and trainers, with her hair up. I see the shock in his eyes – “Oh, wow, she’s totally ordinary.” He won’t think that once he’s heard what I have to say. Still, if he’s read any of my books, he’ll know that my whole creative project is to demonstrate that there is no such thing as normal – not for celebrities and not for nobodies. There is an unwholesome freakishness to everyone and everything, lying just beneath the surface. Seth is about to encounter mine.

“Hi,” he says. “Sorry, I–”

“No worries,” I tell him. “Have a seat. There’s a bottle of red wine on the way.”

We exchange pleasantries for a few minutes and then he looks awkward again as he prepares to refer to the unsavoury business he wishes he didn’t have to acknowledge. He can’t pretend not to have heard about it, though – everybody heard about it; it made the national press. Seth knows he must mention it in order not to seem callous. “I was sorry to hear about your… that thing with the sci-fi writer,” he says.

“My plagiarist?” I smile.

“Yeah. What’s his name again? Paul… something?”

“Patrick Cussons.”

“That’s it. What a cock! And… well, poor you.”

“You know, that’s the part I’ve never been able to fathom,” I tell him. “The Poor Me part. I sell hundreds of thousands of books and earn a million quid a year – I’m fine. Do you know what Cussons stole from my book and put in his?”

“Article I read said several chapters,” says Seth.

I shake my head. “Not true. That’s social media exaggeration for you. He stole one paragraph. That’s it. A long paragraph, but only one. About the difficulty of feeling jolly to order. At Christmas.”

“Oh. Right.”

“And for stealing one paragraph, he gets his book pulped, dumped by his agent and publisher, vilified in the press, massive exaggeration of his crime, people desperately trying to dig up any other grim stories about him they can find and broadcast them to the world. You know he got death threats? For weeks.”

“Right.” Seth looks solemn. And confused.

“Thing is, he apologised,” I point out a feature of the situation that Cussons’ detractors prefer to ignore. “Immediately. He admitted it, said sorry, meant it. And no one forgave him,” I say bitterly.

“Except you, by the sound of it.”

“Here’s my take on it,” I say. “Stealing a paragraph from another writer’s book – yeah, it’s dishonest and stupid. Self-righteously launching a campaign to destroy a guy’s life and career just because he once – once! – made a mistake? That’s… well, that’s despicable. And that’s what the holier-than-thou brigade have done to Cussons. Which is where you come in,” I grin at Seth.

“Me?”

“Tell me this: how easy would it be to fake, retrospectively, email evidence of an affair?”

“You mean…”

“Messages going back years, charting the progress of a love affair. A sexual obsession, maybe – that would be fun.”

“Fun?” Seth looks terrified.

“This is confidential, okay? Whether you agree to help or not, you don’t say a word to anyone. I’ve got the agreement of my husband, my agent, my publishers, Cussons and his wife. All we need is you.”

Seth shakes his head. “I’m not sure what you’re driving at,” he says.

“Let’s say Patrick Cussons and I have been having a secret affair for years. We’re madly in love. Let’s say what he did wasn’t plagiarism at all – we wrote that paragraph together, planning to put it in both our new books. Mine happened to get published first, that’s all. We never expected anyone to notice – it was a harmless private joke. When the scandal broke, Patrick heroically allowed himself to be branded a plagiarist, to protect my reputation and both our marriages. Do you see?” I lean forward. “Look, I’m willing to delay my next book and spend the next few months writing the “affair” email correspondence, if you can somehow… embed it on my computer in a way that looks as if it’s real and goes back years. Then it can fall into the wrong hands,” I say pointedly, “and be the new scandalous story. And rescue Patrick’s reputation.”

“But… what about your reputation?” Seth asks.

I smile. He’s so sweet. “My reputation is for understanding the dark side of human nature. How could I understand it with no first-hand experience? I owe it to my readers to scheme and lie – they’d expect nothing less. I plan to say so, charmingly, in many colour supplement interviews.”

I plan, also, to have the next six months off work – a much-needed rest. The affair email correspondence has, of course, already been written – in real time. (Please don’t tell me that comes as a shock, or I might have to roll my eyes.) I’ve persuaded my editor that this new scandal will give my next book such a boost that delaying the publication date will be worth it. There’s no downside to affair publicity, really, when your husband knows – or thinks he knows – that you’re only pretending to have cheated on him in order to save a fellow writer’s career, because you’re a compassionate person who hates injustice.

I sit and wait for Seth to tell me whether he’s willing to plant on my computer the 120,000 words of love affair that I removed from it yesterday, after saving the text into Word files and printing it all out. Exactly the same word count as one of my novels.

Kind Of Cruel by Sophie Hannah (£7.99, Hodder) is out now

Illustrations: Daniela Jaglenka Terrazzini

Click here to read other Christmas stories written exclusively for Stylist

My Plagiarist by Sophie Hannah