Caleb Carr, a military historian and author whose experience of childhood abuse drove him to explore the roots of violence — most famously in his 1994 best seller, “The Alienist,” a period thriller about the hunt for a serial killer in 19th-century Manhattan — died on Thursday at his home in Cherry Plains, N.Y. He was 68.

The cause was cancer, his brother Ethan Carr said.

Mr. Carr was 39 when he published “The Alienist,” an atmospheric detective story about a child psychiatrist — or an alienist, as those who studied the mind were called in the 1890s — who investigates the murders of young male prostitutes by using forensic psychiatry, which was an unorthodox method at the time.

Mr. Carr had first pitched the book as nonfiction; it wasn’t, but it read that way because of the exhaustive research he did into the period. He rendered the dank horrors of Manhattan’s tenement life, its sadistic gangs and the seedy brothels that were peddling children, as well as the city’s lush hubs of power, like Delmonico’s restaurant. And he peopled his novel with historical figures like Theodore Roosevelt, who was New York’s reforming police commissioner before his years in the White House. Even Jacob Riis had a cameo.

Mr. Carr had also been a regular contributor to the letters page of The New York Times; he notably once chastised Henry Kissinger for what Mr. Carr characterized as his outdated theories of international diplomacy. He was 19 at the time.

“The Alienist” was an immediate hit and earned glowing reviews. Even before it was published, the movie rights were snapped up by the producer Scott Rudin for half a million dollars. (The paperback rights sold for more than a million.)

“You can practically hear the clip-clop of horses’ hooves echoing down old Broadway,” Christopher Lehmann-Haupt wrote in his review in The Times. “You can taste the good food at Delmonico’s. You can smell the fear in the air.”

Magazine writers were captivated by Mr. Carr’s downtown cool — he lived on the Lower East Side of Manhattan, had been in a local punk band, wore black high-top sneakers and had shoulder-length hair — and by his literary provenance. His father was Lucien Carr, a journalist who was muse to and best friends with Beat royalty: the writers Jack Kerouac, William S. Burroughs and Allen Ginsberg. Beautiful and charismatic as a young man, “Lou was the glue,” Ginsberg once said, that held the group together.

The elder Mr. Carr was also an alcoholic, and Caleb grew up in bohemian chaos. The Carr household was the scene of drunken revelries, and much worse. Mr. Carr raged at his wife and three sons. But he directed his most terrifying outbursts at Caleb, his middle child, whom he singled out for physical abuse.

Caleb’s parents divorced when he was 8. But the beatings continued for years.

“There’s no question that I have a lifelong fascination with violence,” Caleb Carr told Stephen Dubner of New York magazine in 1994, just before “The Alienist” was published, explaining not just the engine for the book but why he was drawn to military history. “Part of it was a desire to find violence that was, in the first place, directed toward some purposeful end, and second, governed by a definable ethical code. And I think it’s fairly obvious why I would want to do that.”

Lucien Carr had also been abused. Growing up in St. Louis, he was sexually molested by his Boy Scout master, a man named David Kammerer who followed him to the East Coast, where Lucien entered Columbia University and met Kerouac, Ginsberg and Burroughs. One drunken night in 1944, Mr. Carr killed his longtime predator in Riverside Park, stabbing him with his Boy Scout knife and rolling him into the Hudson River. Kerouac helped him dispose of the knife. Lucien turned himself in the next day and served two years for manslaughter in a reformatory.

The killing was a cause célèbre, and became a kind of origin story for the history of the Beats. Kerouac and Burroughs rendered it in purple prose in a novel they archly titled “And the Hippos Were Boiled in Their Tanks,” which was rejected by publishers and then mired in legalities before finally being published in 2008, when all the principals were dead. (It was panned by Michiko Kakutani in The Times.) In 2013, it was the subject of a film, “Kill Your Darlings,” starring Daniel Radcliffe as Allen Ginsberg.

Caleb Carr and his family found “Kill Your Darlings” more than flawed, taking issue with the film’s thesis that Lucien was a conflicted gay man in a repressive society — and that Kammerer was the victim and their relationship was consensual.

“My father fit perfectly ‘the cycle of abuse,’” Mr. Carr told an interviewer at the time. “Of all the terrible things that Kammerer did, perhaps the worst was to teach him this, to teach him that the most fundamental way to form bonds was through abuse.”

He added: “When I confronted him many years later about his extreme violence toward me, after I had entered therapy, he at length asked (after denying that such violence had occurred for as long as he could, then conceding it), ‘Doesn’t that mean that there’s a special bond between us?’ And I remember that my blood had never run quite that cold.”

Caleb Carr was born on Aug. 2, 1955, in Manhattan. His father, after being released from the reformatory, worked as a reporter and editor for United Press International, where he met Francesca von Hartz, a reporter. They married in 1952 and had three sons, Simon, Caleb and Ethan. After they divorced a decade later, Ms. von Hartz married John Speicher, an editor and novelist with three daughters. The couple and their six children moved to a loft on East 14th Street, a dangerous area in the late 1960s and ’70s. It was another chaotic household overseen by alcoholics, and the children often referred to themselves as “the dark Brady Bunch.”

Caleb attended Friends Seminary, a Quaker school in the East Village, where his interest in military history made him an outlier and a misfit. His high school transcript described him as “socially undesirable.” After graduating, he attended Kenyon College in Ohio and then New York University, where he earned a bachelor’s degree and studied military and diplomatic history.

In 1997, Mr. Carr published “The Angel of Darkness,” a sequel to “The Alienist.” It featured many of the same characters, who reunite to investigate the case of a missing child. It, too, was a best seller, “as winning a historical thriller” as its predecessor, The Times’s Mr. Lehmann-Haupt wrote.

Mr. Carr was the author of 11 books, including “The Italian Secretary” (2005), a Sherlock Holmes mystery commissioned by the estate of Arthur Conan Doyle; “Surrender, New York” (2016), a well-reviewed contemporary crime procedural that nonetheless sold poorly; and “Lessons of Terror: A History of Warfare Against Civilians” (2002), which he wrote in the wake of the Sept. 11 attacks.

Even in those pre-Twitter days, “Lessons of Terror” caused an internet ruckus. It was at once vociferously praised and bashed — and became a best seller, to boot — and Mr. Carr derided his critics on Amazon. Many challenged his contention that some “conventional” warfare — like General Sherman’s barbarism during the Civil War and Israel’s behavior toward the Palestinians — was equivalent to terrorism, a thesis that annoyed military historians, as well as The Times’s Ms. Kakutani.

What propelled Mr. Carr in all his work was the origins of violence, the mysteries of nature and nurture. In his own life, he was determined to end the cycle of his family’s dark legacy by not having children. That choice restricted his romantic life, and as he got older, he grew more solitary. When he bought 1,400 acres in Rensselaer County, N.Y., in 2000, and built himself a house near a ridge called Misery Mountain, he became even more so.

“I have a grim outlook on the world, and in particular on humanity,” he told Joyce Wadler of The Times in 2005. “I spent years denying it, but I am very misanthropic. And I live alone on a mountain for a reason.”

His last book, published in April, was “My Beloved Monster: Masha, the Half-Wild Rescue Cat Who Rescued Me.” It’s both a memoir of his time there and a love story to the creature who was his most constant and sustaining companion during the last decades of his life.

“But how could you live for such a long time,” he said friends asked him, “alone on a mountain with just a cat?” He took umbrage at the phrase “just a cat.”

“It needs to be understood that, for Masha, I was always enough,” he wrote. “How I lived, what I chose to do, my very nature — all were good enough for her.”

Masha, like her human roommate, had suffered physical abuse at some point, and as Mr. Carr and his companion aged, their early horrors had devastating physical repercussions. Mr. Carr’s beatings had created scar tissue in his organs that led to other serious ailments. They were each diagnosed with cancer, but Masha died first.

In addition to his brother Ethan, Mr. Carr is survived by another brother, Simon; his stepsisters, Hilda, Jennifer and Christine Speicher; and his mother, now known as Francesca Cote. Lucien Carr died in 2005.

Despite the early hoopla, “The Alienist” never made it to the big screen. Producers wanted to turn it into a love story or otherwise alter Mr. Carr’s creation. But after decades of fits and starts, it found a home on television, and in 2018 it was seen as a 10-episode mini-series on TNT. James Poniewozik of The Times called it “lush, moody, a bit stiff.” But it was mostly a success, reaching 50 million viewers and earning six Emmy Award nominations. (It won one, for special visual effects.)

“If I had known that nothing would have come out of this book other than the advance,” Mr. Carr said in 1994 as “The Alienist” was poised for publication, “I still would have written it exactly the same. But if you were to ask me to trade this book, this whole career and have my childhood be different, I probably would.”