My mother raised her hand to her chest and started to rub hard with the knuckles of her right hand into the soothing worry stone of her sternum.

His lower limbs jerked once, then twice.

She put her left hand on top of our mailbox to steady herself. She was six feet away from him.

“Billy?” she whispered.

The doctor said later that if mercy had been attending him, he would have been walking. That way, the car would have hit him head-on and lower to the ground. Whoosh, he would be plowed down-dead immediately.

I’ve always wondered what he must have thought during those final minutes as my mother stood so close to him. How could the world change so fast? Could he know, at eight, what death was? Cars came out of nowhere and hit you two houses down from where you had grown up, and a woman who had always seemed just a typical adult, in those rare moments you saw her in her yard, stood at the edge of the road but did not comfort you. Was this punishment for having stayed home sick from school? For having broken the rule of remaining in the house while your mother was gone?

I was sixteen. Natalie and I would put on Danskin unitards and make up dance routines in her parents’ refurbished basement. We used her father’s circular bar to propel us across the room, where we perfected a tumbling routine involving the long, low couch and the bearskin rug on the floor. Our dances were narrative and sweaty, and contained sit-ups and leg lifts that cropped up out of nowhere.

“He didn’t wonder anything,” Natalie tried to reassure me in the days to come.

By the time I got home, his body was gone, but I could still see the long stain that smeared the pavement like an exclamation mark. “His brains were smashed,” Natalie said. “He wasn’t thinking anything.”

But I had listened to my mother sobbing in my father’s arms. “He called me ‘ma’am,’ ” my mother said over and over again. “He looked across at me and called me ‘ma’am.’ ”

My father, who, if not exactly social, was roundly liked in the neighborhood for his hellos and his courtly manner when he ran into the neighbors at the local grocery, had tried to explain my mother’s inability to walk into the road.

“Why didn’t she call someone, then?” asked Mr. Tolliver, who lived around the corner and led his own wife on humiliating walks in which he forced her to pump her arms and raise her legs high like a one-woman marching band. “Mrs. Tolliver is a rounded woman,” my mother said. “He shouldn’t have married a rounded girl if he didn’t want a rounded wife.”

“Clair was frozen,” my father explained. “Literally frozen to the spot. She couldn’t help him.”

As the men and women of the neighborhood drove home from work, they were stopped by police and told to park their cars and walk or, if it made more sense, to circle around in the opposite direction. But most of them parked their cars and got out, joining the crowd that stood on the Beckfords’ lawn across the street.

They were angrier, it seemed, at my mother than at the faceless, nameless stranger who had mown Billy Murdoch down. It took every person who joined the group two or three times hearing the story before they understood how what my mother had done was possible. And it wasn’t exactly that they understood. It was more like, by rote, it began to sink in. Clair Knightly, whose husband they all knew, had stood in her yard and watched a boy they all knew die. She did not help. She did not go to him. None of them asked what his parents would wonder for years: Did Clair Knightly even speak to him? Did she say anything?

The answer was that my mother both wept and sang.

She stood at the edge of her property and rubbed her chest furiously, back and forth with the sharp knuckles of her right hand. Her left hand flitted from her head down to her side.

“Billy,” she said over and over again, as if naming him might pull him closer.

His head was on the road, and it was facing her. His eyes were open. She saw his mouth moving but couldn’t get herself to stop repeating his name in order to hear what he had to say. By saying “Billy,” she was keeping herself in the present, anchoring herself there by the mailbox. Instinctively she knew this was what she must do if she was going to try to help him.

When there was a break in her rhythm, she heard him.

“Ma’am?”

That was the moment she knew she wouldn’t be able to do it. She didn’t bother saying his name anymore. She stared at him. She stayed right where she was, kneading and rubbing her chest until, as she revealed to my father two days later, she had rubbed a bloody cavity from her throat to her breastbone.

The other thing the neighbors never found out was the song my mother sang him. It was a song that, whenever I heard it coming through the vent that led from her bedroom to the bathroom, put me on guard for the advent of a bad day. It was a rhyme she remembered from childhood, and she would sing it repeatedly, the words running together into a sort of chant.

Posies are bright, clear, and gay.

Daffodils sprout on the lawn in May.

Flowers and girls are often the same.

Rose, Violet, and Iris are names.

She would hum the next few lines, whose words, I assumed, she had forgotten long before. It soothed her, and I knew this, but when I went to her bedroom to ask if she needed anything, I would remain in the doorway until her lips stilled.

My mother sang and hummed this song to Billy Murdoch until a delivery truck drove up, heading for the Levertons’, who, in celebration of their wedding anniversary, had already left the day before on a trip. The young man, in white coveralls and a ponytail, leaped out and in a flurry ran past my mother. He bolted up the stairs through our open door, found the phone on the side table in the family room just next to the couch piled with half-sorted boxers and socks, and called the hospital.

By the time the ambulance and the police arrived, Billy was almost gone, and everyone had questions for the incoherent woman singing an incoherent song.

After that, we kept the blinds drawn and pretended the trash on our lawn had fallen there by accident. I stayed away from school for six weeks. I would meet Natalie on a wooden bench in the park five blocks from our house.

“Not yet,” she’d tell me, and hand me the assignments I’d missed. Even her parents preferred not to have me come over to her house anymore.

“I hate this,” I said.

“Remember Anne Frank?” Natalie said once. “Pretend you’re like her, and you can’t go anywhere until you get the all clear.”

“Anne Frank was exterminated!”

“Well, not that part,” Natalie said.

I began to spend my time calculating. I was a junior. I had eighteen months to go until, somehow, I would get out.

I did not tell my mother this. At home, all roads revolved around her more than they had before. My father and I whispered our hellos in those first six months after Billy died, and when the doorbell rang, we scurried like mice into dark corners, hoping whoever it was would go away. A rock came through the front window once, and we hid this fact from my mother, claiming instead that it had been my father reaching back to turn the page of a newspaper and poking his elbow through the glass. “Can you believe that?” he said with his best variety-show voice. “I didn’t know I was that strong!”

“Or that oblivious,” my mother said, weakly playing her part of condemning him, though we all felt the lack of her sharp tongue. Judgment, her savior and guardian, had left her. Her perch at the window of the living room, from which she could watch Mrs. Tolliver marching by or call the next-door neighbor’s child a slut, was cloaked in a heavy wool curtain that we ceased to open.