It was easy to miss. Susan Toler Carr and her husband, Darrell, were picking through the charred remnants of what had been their home when she spotted a speck of turquoise in the blackened debris: a small metal butterfly, untouched, it seemed, by the fire that had torn through their quiet neighborhood at the foot of the San Gabriel Mountains.

Almost nothing was left of their house. But the butterfly was among the signs that cemented their resolve to stay. This was still home.

The thousands who have lost so much in the Los Angeles wildfires will soon wrestle with how to rebuild the lives that perished with their homes. Leave the neighborhood? Leave the city? The decisions will be personal. For the Carrs, the calculus has particularly deep roots.

Their century-old Spanish Colonial Revival home in Altadena, where they have lived for nearly 25 years, was not just a roof over their heads. It was a place where they had raised their only son, Justin, who was an aspiring architect, an accomplished swimmer, a lyrical poet, a winsome tenor and a painting prodigy.

And it was where they continued to feel his presence, years after he had died at the age of 16, from a sudden and rare heart condition.

To his parents, Justin had remained in the bedroom they had maintained since his death in 2013, in the paint colors he had picked out for the house, in his art on the walls, in the poems he put down on paper and in every manner of butterfly that presented itself — a motif that represented his favorite swimming stroke.

Almost everything was now gone, and yet almost everywhere, memories remained.

“I feel like part of my life went up in smoke,” Mrs. Toler Carr said on Saturday as she prepared to walk around the remains of the house, heat still radiating from the wreckage.

In Los Angeles County, a sprawling region that has long lacked a center, the fires have connected neighborhoods that otherwise had little binding them. Altadena, a racially diverse, middle-class community in the inland shadow of Pasadena, and Pacific Palisades, with its ocean breezes, sublime views and tear-downs starting in the millions, had little in common until they were both ravaged by the fires.

Justin Carr might have grown to be another link.

Earlier generations of his family had been part of a wave of Black people who moved from the South to California, where many settled in the Los Angeles area seeking better jobs and a better life. Mr. Carr’s father had grown up alongside Jackie Robinson in Pasadena. Mrs. Toler Carr’s father, Burl Toler, became the N.F.L.’s first Black referee in 1965. When Justin was a year old, his grandmother looked into his calm, inquisitive eyes and observed: “Oooh, this boy has been here before.”

Justin attended Harvard-Westlake, an exclusive private school with a small population of Black students. In a poem that he wrote for a class and that his parents were presented with after he died, Justin wrote that walking down white halls with white walls, “with kinks in my hair and the dark skin I wear,” left him feeling like a fly in a bowl of milk. He made sure to sit in the front row in class, he wrote, because “it’s hard for me to imagine being stationed in the back, just like my mother and father were, where they couldn’t even see that they were lacking opportunity.”

On the daily bus ride to Harvard-Westlake, 20 miles to the west, Justin struck up a friendship with another Black student, a baseball player. After the baseball team attended Justin’s memorial service, which drew close to 2,000 people, his friend pitched a no-hitter that very afternoon. He told a reporter that he had been thinking of Justin when he took the mound. (Last fall, Justin’s old friend, Jack Flaherty, helped pitch the Los Angeles Dodgers to a World Series championship.)

Justin had been at swimming practice when he went into cardiac arrest, prompted by an undiagnosed heart condition. He was rushed to the hospital, but could not be revived.

Days later, his father had a heart attack.

When Mr. Carr’s older brother picked him up at the hospital to take him to the funeral home to make arrangements, he confided that he didn’t want to live. His brother stopped the car and told Mr. Carr that it was his responsibility to carry on his son’s dreams.

“I was just as limp and as numb as I could be,” Mr. Carr said. “I didn’t know what he was talking about for days, but he made me think, as my older brother makes me really dig in my brain.”

Then it came to him.

At Justin’s memorial service, Mr. Carr recalled the first time he had asked his son to say grace. Justin was 4. He asked God to bless his mother, father, grandfather, a seemingly endless list of cousins, aunts, uncles, classmates, neighbors and pets, before finally — supper was getting cold — asking the Lord for one last thing: world peace.

“I thought, Who am I sitting next to?” Mr. Carr said with a laugh. “Gandhi? Martin Luther King? Medgar Evers?”

The moment became the inspiration for the Justin Carr Wants World Peace Foundation, which offers creative art programs and scholarships, heart screenings and cardiac event training, and peace-building workshops. The foundation’s logo is a silhouette of Justin flashing a peace sign, made from a photo taken by his father.

The Carrs have found purpose in the foundation.

Mrs. Toler Carr, a retired civil engineer who helped design theme parks for Disney and Universal Studios, attended a weekly grief group for five years — in Pacific Palisades, of all places — and said writing has been therapeutic. Mr. Carr, who taught photography, metalworking and auto shop at high schools and community colleges, has found his own peace.

“There are no stages of grief,” he said, explaining that he has gotten better at managing the pain. “When people ask how I am, I say ‘I am.’”

When the Carrs were alerted by neighbors that the flames from the fire in Eaton Canyon were racing toward their neighborhood, they hustled around the house, gathering up what they could and loading it into their S.U.V. They pulled Justin’s artwork from the walls, packed up boxes of his belongings and, in less than an hour, drove off to a friend’s home 15 miles away in Toluca Lake, where they have been staying since.

They returned the next day and saw what they had left behind. The melted filing cabinets that contained Mr. Carr’s three Contax cameras, his Zeiss lenses and the years of negatives — all priceless. “A photo is a presentation of time, a recording of history that’s never going to happen again,” he said, stifling tears. The verdant backyard where they could take in views of the towering mountains had turned to rubble. The neighborhood, where they knew people by the houses they lived in and the cars they drove, was desolate.

“I’d cry a bucket of tears, but I’m all empty,” Mrs. Toler Carr said during a subsequent visit on Saturday.

Over here was the kitchen. Over there was the patch of milkweed, a magnet for butterflies. The brick chimney, with the herringbone pattern that Justin had designed, still stood. So did the driveway gate, crafted by a former student turned metalworker who had surprised the Carrs with the design. Arched across the top were the words Justin Carr Wants World Peace.

“That gate is a symbol of Justin’s strength,” his father said. “Something to lean on for a new beginning.”