There was a dead mouse in Mum's bedroom.
Simon gently pushed the door open and crept in. He smelled his mother's perfume, almost overwhelmed by the odour of sweat and cigarettes and sour alcohol. A ray of morning sunlight shone through the curtains like a spotlight, illuminating a snoring shape under the covers. Simon was always surprised by how small Matt looked when he wasn't shouting. His feet didn't even reach the end of the bed, but fell short by — well, a foot.
I once knew a woman who told me that her cat kept bringing in dead mice, and because she was rather squeamish, she paid her son 75p to dispose of each corpse. This set my story antennae tingling — the situation was ripe for escalation, and I only needed to decide how far to go.... All the way, of course! Once my source had been transposed into fiction and provided with a sinister boyfriend, the plot of the story became obvious.
With a straightforward tale, it's necessary to include sufficient characterisation and metaphor to retain the reader's interest. I gave the mother in the story a background as a magician's assistant, while her young son aspired to follow her into show business and become a magician himself. The props and aura of stage magic — the tricks and disappearances — provided a unifying theme to flesh out the bones of the basic "dispose of the bad guy" plot.
The completed story contained no fantastical elements, so I couldn't send it to the usual SF & Fantasy venues. I marketed it as literary fiction, and also as horror, and eventually it was picked up by the webzine Gothic.Net, which in those days paid five cents per word and was an SFWA-qualifying market. SFWA is the science fiction and fantasy writers' association; I found it amusing that my first SFWA-qualifying sale was not actually SF or Fantasy.
One drawback of being a British writer is that most of the markets are American, which means that using any elements of British culture or language can be problematic. I usually workshop my stories, and it's surprising how many Americans are apparently unwilling to engage with foreign usage. It seems that American readers will happily project their imaginations to other worlds and future aeons, but will take umbrage at an expression that comes from a mere ocean away. After I workshopped the first draft of "House Cleaning" at Critters, I removed several elements that Americans quibbled with. Nevertheless, apparently enough remained that the Gothic.Net editor felt it necessary to say, "One of the problems we face with submissions is colloquialism, use of certain phrases from a given region that may not be universally understood by our readers. With that in mind, I'd like to suggest the following changes...."
It's difficult, and frustrating, to write a story set in Britain without being allowed to use any British expressions. It dilutes the atmosphere of the story, and diminishes the "aura of authenticity" that's crucial to the story's effect. I expect that even Stephen King might have trouble if he wasn't allowed to use any Americanisms when writing a story set in an American small town.
This is less of an issue when writing about other worlds and future aeons, because those aren't specifically British or American, and hence it matters less whether British or American English is used. The paradoxical effect is that it's easier for me to write — and sell — a story set on an alien planet than one set in the land where I live.
Fortunately, not all American markets are quite so parochial. I subsequently resold the story to Plan B, who were happy to publish my original submission draft, without requesting any dilution of the language or setting.
Incidentally, Plan B describe themselves as "a magazine devoted to mystery and crime short fiction". The fact that I sold the same story to a horror magazine and a mystery magazine shows that genre categories can be rather fuzzy.