“We all partied together,” he said.

The older Mr. Winemiller said his daughter’s drug use was rooted in anxieties, stresses and an academic and social tailspin that began in high school. She had been in recovery for about three years when she began to use again early last year, he said.

She came to stay at the farmhouse on March 26, a day after three acquaintances of hers were arrested on heroin charges at a motel in the nearby town of Hillsboro. He said he went to the garage to get her a Coke, she excused herself to the bathroom, and he was overcome by a terrible dread when he sat back down in the living room.

“I knocked on the door, and there was no answer,” he said.

At her funeral, the younger Mr. Winemiller said, the two brothers stood by the coffin, “telling each other how we had to make it for our parents.”

Paul Casteel, the senior minister at the Blanchester Church of Christ, conducted the services at Eugene Winemiller’s funeral. The next day, he led another funeral for another man who had died of an overdose.

People live here because they like knowing their neighbors and raising their children close to extended families, Mr. Casteel said. But heroin has turned that small-town closeness on its head.

“When somebody ends up into drugs, you’re going to know them,” he said. “You know everybody. To be honest, I wanted to stay out of it, just concentrate on the church. But we just kept getting hit.”

By early afternoon, the father and son, done with their appointments, climbed into the Tahoe and headed home down State Route 380. They smoked and listened to contemporary country play softly on the radio, and made plans for their next trip to the probation office in two days’ time.