In The Haunting of Alma Fielding (Penguin Press, Apr.), Summerscale delves into the story of an Englishwoman whose home was reported to be plagued by supernatural spirits in the 1930s.

How did you first hear of Nandor Fodor, the psychic investigator who looked into the case?

I wanted to write about a haunting, and I started reading anthologies. It was a complete surprise to me that there was a boom in séances and ghost sightings in Britain between the wars. When I read about Fodor in an academic book, which mentioned Alma’s case, I realized that he was bringing Freudian ideas to bear in this territory. It seemed like a very enticing combination, how those things intersected—the psychoanalytic and the psychic.

What did that boom indicate about that period?

I’m always interested in slices of history that illuminate what people are feeling, as well as thinking, and the way that the national mood can get under people’s skin. Ghosts and spooks were expressions of anxiety. They can crystallize the ways in which people are suffering from pain from the tremendous loss of life from the First World War, and the Spanish flu, which set in motion all the séances and the ghost sightings. There was also suspense and anxiety about whether war was about to come to Britain, and I think these things often express themselves indirectly. So the ghosts were sort of imaginative projections of people’s inner worlds, the way people connect to the anxieties and fears that they’re feeling. I think that in some ways the psychoanalytic interpretation tapped into that.

Did you learn anything significant from interviewing Fielding’s grandson?

I found Alma’s grandson, Barry, in Devon. He showed me his family photograph albums, and I saw the picture of Alma’s son, who died when he was a baby. I had noticed that many of the women reporting psychic phenomena in the 1930s had suffered horrible bereavements, and it seemed to me that a lot of what Alma was playing out in the séances she’d faked was connected to this kind of grief. Through Barry, I found material that changed my interpretation of she had been going through.

Why did you subtitle your book A True Ghost Story?

It’s a nonfiction book, a historical story, so in that sense it’s true. Whether it is true as in whether there were real ghosts of the dead is something for the reader to decide. Whether it expresses a truth about the haunted character of Alma Fielding could be another form of truth. So I think it’s a slightly provocative subtitle that captures something about what I wondered about—what would make a ghost story true.