Some years ago, Dani Shapiro's husband and son were driving home from a townball game when teenagers threw a bottle of salad dressing from the top of an embankment. It shattered in the street, missing their car by a fraction of an inch.
"When my husband got home he told me if it had been a second earlier, that salad dressing would have hit the windshield and they would have had a terrible accident," Shapiro said in an interview from her home in Connecticut. "And I thought, salad dressing! I never considered a bottle of salad dressing becoming a means of devastation."
The lesson from this — the lesson that Shapiro already knew, thinks deeply about and has woven into her new novel, "Signal Fires" — is that randomness, chance, quick decisions to turn left or right, to pause or accelerate, can change a life in an instant.
"It's something that comes up again and again in the novel," said Shapiro, who will be in St. Paul for Talking Volumes on Oct. 28.
"Everything we do matters. And if we thought about that all the time we wouldn't be able to get out of bed. But if we actually internalize that to some degree I think it can define what it is to be a human being."

Shapiro, 60, is as well known for her bestselling memoirs as she is for her novels. She is also the host of the podcast "Family Secrets," which explores long-buried secrets and the liberation that comes from setting them free.
"One of the things I've learned is that when there is a secret that is being kept, there is shame," she said.
Secrets suffuse "Signal Fires," which opens in 1985 when a teenage girl tosses her car keys to her younger brother. She has been drinking, but he doesn't know how to drive, and the result is a crash and a terrible death. The rest of the novel deals in various ways with the repercussions from that choice — including the psychic pain of silence.