Citing master of horror Stephen King and Woman In Black author Susan Hill as prime examples, Welsh is intrigued by how old buildings can apparently absorb resonances of past traumatic events that have happened within their walls.
"How would you feel if you found out that something really bad has happened in your house?" she says. "People don't want to buy houses where something awful has happened. You wouldn't want to buy Rose and Fred West's house, but why not? It's just a place and yet it conjures up something within our imaginations."
Welsh had a similar feeling when, like Jane and Petra, she and her partner, Scottish author Zoe Strachan, moved to Berlin for several months. "It was for the summer, so it was very different from the book," she says. "I was thinking about the people who used to live in our building and where did they go? We lived very close to the Jewish cemetery and there was an art project nearby, where this artist had looked up the names of every person who had been murdered there during World War II, then written them down on these little brass cobblestones. It was that idea of, 'how much should we remember and how much of that memory is useful?' But at the same time, young German people have to live as well. They can't be paralysed with guilt for something they didn't do."
Welsh admits she takes some guilty pleasure from watching unsettling, spooky films that keep her awake at night. "I like strong narrative, so I'm a sucker for all that kind of stuff," she laughs. "I really enjoy a good scary movie but I don't like blood and gore. It's funny because I've written about the gothic tradition and read a lot of theory about it but ultimately it still works on me. I actually get scared and that's why I want to read it or write it. I'm not even sure why we want to be scared but maybe it's a kind of high."
According to Welsh, such visceral thrills evoke very elemental feelings in us all. "When I think back to the Picts or the early folk who were living on Skara Brae in the Orkney Islands, which is one of my favourite places, I imagine them sitting in their wee houses and being scared of the same things we're also scared of, such as the dark or the idea of somebody, not necessarily a ghost, being outside," she says. "All of that stuff is international as we're scared of the same things that people in Taiwan are scared of. We all worry about the dead rising up and walking about."
With its cover featuring a young child in a bright red coat, The Girl On The Stairs acknowledges the debt it owes to Nicolas Roeg's cult film Don't Look Now, which starred Donald Sutherland and Julie Christie as bereaved parents who encounter a similarly mysterious figure during a trip to Venice.
"It was not so much the story but the atmosphere I was interested in," says Welsh, who was also influenced by Roman Polanski's similarly suspenseful 1960s movies Repulsion and Rosemary's Baby. "I didn't go back and look at them again, which is a decision you always have to make. You have to decide whether you view these things again or work from your memories, which, of course, can be inaccurate."
The Girl On The Stairs (Hachette $36.99) is out now.