Alice Morgan is becoming accustomed to unsettling audiences with the characters she portrays, she tells Laura Harding

RUTH WILSON is used to alarming audiences. She played the deeply unsettling Alice Morgan on BBC's hit drama Luther on and off for six years.

But her new film, The Little Stranger, an adaptation of Sarah Waters' 2009 novel of the same name, offers more than just a parent-killing psychopath. It is instead a chilling Gothic thriller set in a sinister house where mysterious writing appears on walls and bells ring without human intervention. And for Wilson the source of the mystery at the heart of the story proved endlessly fascinating.

"There is something about repression in this society and the repression of feelings, repression of desires, that exists in all the characters on the screen," she says. "If you repress something that much, it might come out in some kind of energy or form emanating from something darker in individuals. I don't think it's a physical being necessarily doing things, it's something supernatural. It's odd, but it's not defined so it's left to the audience."

Set in the summer of 1948, the story follows Faraday, a doctor played by Domhnall Gleeson, who is summoned to the stately Hundreds Hall to examine a young maid. It is the first time he has seen the house since he attended a fete there as a child in 1919. At the time, the working class boy was overwhelmed by its grandeur and beauty and jealous of the beautiful little girl who lived there, so much so that on impulse he snapped off a plaster acorn from one of the mouldings in the ornate entrance hall.

On his return, his find the house has fallen into disrepair, as have the Ayres family who occupy it. They are part of the landed gentry subjected to the high taxes of the new Labour government and Wilson plays Caroline Ayres, who is attempting to keep the house going alongside her brother Rod, played by Will Poulter, who has been left badly disfigured by fighting in the war.

As Faraday becomes more closely entangled with the family and more enthralled by the house, unsettling things begin to happen. And while the story can be seen as a haunted house story, Wilson discovered new depths to it after she finished filming.

"Actually this is about patriarchy," she says, "about the oppressive environment that the class system created and still does and what women were oppressed by and in. Caroline has just been in the war and tasted freedom and had economic freedom, and then is suddenly thrust back into a social construct which she wanted out of, having to go back to traditional female roles. Even this man, that she thinks might be her escape route, is also trying to impose those constraints on her."

She pauses for a moment. "There is something about property and ownership too. This house is falling apart and these people can't look after it anymore and they can't afford to keep it up. Faraday is determined at whatever lengths to have this place or to maintain it and to have ownership over it."

Watching the film back now, in a post-Weinstein world, the storyline smacks of toxic masculinity.

"When we were doing it, it didn't really strike out to me that that was what it was about," she says thoughtfully. "But watching it, I was like, 'That is definitely a theme that is inside it' and of course Sarah was dealing with that in the book. It's just now that we are all becoming much more aware of that and alert to those kind of attitudes."

Gleeson agrees, saying: "There is a lot happening at the moment in an effort to reverse some of the toxic masculinity that is in society and when this happened it was even more rampant than it is now. There were very few ways out for a woman in Ruth's character's situation and this is something that Faraday subconsciously becomes involved with. It's right there in the novel, we haven't put it into the film. Sarah Waters is gifted and knew what she was doing when she wrote the novel. But obviously it's become a much bigger part of the conversation publicly now, which is brilliant."

The film also paints a brutal portrait of the class system in post-war Britain. Faraday, a country doctor, is treated like the help by friends of the Ayres who come for dinner. Caroline's mother makes it clear he should know his place.

"Our country is completely defined by class and still is," Wilson says. "Class is something you're born into and that creates division and that creates envy, creates anger, creates frustration. You have no choice and the film shows that is really divisive and violent-making."

* The Little Stranger is in cinemas now.