For Catherine Lacey, fiction is a vehicle for discovering personal truths.

“When I start trying to make choices about what to reveal or conceal, it just doesn’t work,” the author said in a recent “Writers Speak” event hosted by Harvard’s Mahindra Humanities Center. “When I try to keep [the personal] out, it gets in anyway, or the book will refuse to be written.”

Lacey’s critically acclaimed debut novel “Nobody Is Ever Missing” provides an early example of the writer putting herself in her prose, even subconsciously. In the story, the main character loses her adopted sister to suicide. Between her finishing the book and its publication, Lacey’s stepsister died as a result of substance use — something the author couldn’t have predicted but nonetheless grappled with on the page, she said.

“I didn’t have an adopted sister, I didn’t know anybody that had killed themselves, but my stepsister died by suicide — is the simplest way to describe it — after I had finished the book, and it was something that had been present in my life for about five years before,” she said. “It was present in the family and something everybody knew that they didn’t want to know. And I think those are the kinds of things that come out in fiction when a voice starts to feel like — ‘This is me, but it’s not me’ — and it does feel authentic, but I don’t know where it’s coming from.”