The first ever Cosy Mystery Club letters went into the post in the first week of September, after months of writing, designing, printing, cutting, folding and developing increasingly specific opinions about paper. It was quite strange, and lovely, to see a place that had existed entirely in my head suddenly sitting in a stack of envelopes in a post office in Meath.

I won’t say much about what happens in Month One because some detectives are still at work, and I want these posts to remain completely spoiler-free. But I can tell you a little about the world you’ve just entered.

Avonlea is a crumbling old house in the fictional Meath village of Kells, and the home of January Quail, who some readers will already know. January is the main character in my novel Death Visits January, published by Poolbeg, where she’s an antiques journalist who gets drawn into a murder investigation after a supposedly ancient bog body discovered in Ardee turns out to be considerably more recent.

The January we meet at Avonlea is a few years older and has left newspaper life behind, although she still writes the occasional antiques column. She is now attempting to restore her enormous old house and make it pay for itself, including opening accommodation pods in the grounds which, to her surprise, people are actually willing to pay money to stay in. The roof has almost stopped raining indoors. Progress.

You don’t need to have read the book to join the club, but if you want to meet January before Avonlea, you can find it here: Death Visits January.

I’ve loved building the world around her. Avonlea and all the characters are fictional, but they’re very firmly rooted in Meath, with local newspapers, farmers, auctioneers, taxi drivers, weddings, court cases, football and the sort of people who know exactly what everybody else is doing. Not everything you encounter is necessarily a clue. Some things are simply there because that’s what life in a small town looks like.

One of my favourite pieces in September’s envelope is the Avonlea postcard, designed by Navan artist Meghan McDermott and printed by Excel Print in Navan. I loved the idea that something from a fictional part of Meath should be made here in the real one.

And please use it. The postcard isn’t evidence. Write on it, stick a stamp on it and send it to somebody. I particularly like the thought of Avonlea postcards turning up in letterboxes around Ireland and further afield, and people trying to work out whether the place actually exists.

As for what happens next, October’s letters will be posted in the first week of October and will contain the solution to September’s Month One mystery, along with the next instalment. Going forward, Cosy Mystery Club letters will be posted during the first week of every month.

Until then, write down your theory and sit with it for a while. There is no answer button to press.

You have to wait for the postman. Are you hunting for a hint for month one? Well, I wouldn’t be as misanthropic to withold one.