LOS ANGELES — David Milch sat in a Playa Vista restaurant, eyeing a small cheese pizza in front of him. The story he was telling is true.

“I was running bets for my old man and half a dozen people when I was a boy,” Milch said, flashing a soft smile at the recollection of hanging out at the racetrack. “They’d tell me, ‘Bet $10 on the seven horse and shut up!’ For the big races, it was frightening, carrying around $1,000 when I was 7 years old.”

Encouraged by his companions in the nearly empty restaurant — Rita, his wife of 43 years, and his good friend, John Hallenborg — Milch continued to weave his memories of those bygone days into indelible images: magnificent horses thundering across the finish line and “degenerates” wagering staggering sums.

In many ways, it was a familiar scenario. Telling vivid stories populated with colorful characters, good and not so good, has been the defining work of Milch’s life. That ability made him royalty in Hollywood as he wrote for the classic police procedural “Hill Street Blues” and created provocative fare such as the gritty cop drama “NYPD Blue,” with Steven Bochco, and the acclaimed neo-Western “Deadwood.”

But this was not just a casual lunch to indulge in nostalgia.

While Milch, 78, can still tap into his past to construct a compelling yarn, his thoughts are filtered through a degrading lens. In 2019 he disclosed that he has Alzheimer’s disease. After being at the center of the TV world, his career came to an abrupt halt. Many in the legion of friends and associates who used to surround him when he was a big shot gradually drifted away.

“I’m losing my facilities,” he wrote in his 2022 memoir “Life’s Work,” composed with the help of his wife and children. “I wonder, and not infrequently, ‘Is it gone for good?’ My mind.”

But as he picked at his pizza, Milch demonstrated that his mind is far from “gone.” His vibrant spirit and artistry are thriving in a manner that might surprise the families of those affected by the degenerative disease.

David Milch has a new screenplay.

For more than a year, driven by a dual mission of keeping Milch’s artistic muscles alive and shattering the stigma that shadows those who suffer from dementia and Alzheimer’s disease, Rita and John Hallenborg have established a routine of working lunches intended to stimulate the TV legend’s creative juices.

“Work is at the core of David’s spirit — it’s his essence,” said Rita, sitting next to her husband at one of the lunches. “I really don’t care about the end result or whether this gets made.” The idea, Hallenborg added, “is to keep David engaged and bring him a source of joy.”

The result, a feature called “The Last Horsemen,” could return Milch to the spotlight nearly five years after his last produced credit, “Deadwood: The Movie,” was released.

It’s another unexpected twist in the life journey of Milch, who was known not only for his considerable showbiz triumphs but also his notorious dark side. In addition to being diagnosed with bipolar disease in the early 1990s, his addiction to gambling and drugs did extensive damage — he lost millions at the track and on sports betting. His volatile personality made him feared on and off the set.

“The Last Horsemen” is the realization of a Milch story that was never developed, a narrative set in the horse racing world that centers on a corrupt gangster and his son and their impact on a young couple. Like other Milch projects, it contains raw language, complex relationships and unflinching violence.

Elements of the story came together as Rita was focusing on “Life’s Work.” “David would ramble and tell me stories, and it was often the same story,” she told The Times. “It was often David’s story in different manifestations, and the characters were often him and his father. David was abused as a child. It was like all these things that he’d been working through his whole life.”

“There was the outline of a story he would keep coming back to,” so Rita called Hallenborg, who had worked with Milch on various projects. “I needed someone who could turn that outline into script form,” she added.

She trusted Hallenborg, who had been visiting Milch at the assisted living facility where he now resides. In addition to writing, their bond was built on their mutual love for horse racing — they’d spent numerous afternoons at the track — and their shared experience with addiction.

“Rita told me that David was absolutely animated about this story,” Hallenborg said.

At lunches during the next year, the tale was fleshed out. “We’d ask David, ‘What do you think of this?’ And it will be like the click of a light on his face,” said Rita. “I push ‘record’ on the phone, and it goes from there. It’s jumbled and confused, but in there is a kernel of something that’s real David.”

Rita would email the recording to Hallenborg, who “would take from that the gold that David had mined” and incorporate that with his own voice.

“David, I want to talk today about happiness for gamblers,” Hallenborg said at one outing. “Did you feel happiest when you won at the track, or were you anxious to parlay your winnings back into the game?”

Milch replied that he “didn’t feel any imperative to prove myself again.”

“I think David is happy for a brief time when gambling ... minutes, hours,” offered Rita. “His high was being at risk, having everything on the table.”

“Absolutely,” Milch said.

“When he was happy, I was happy,” Rita continued. “But no, I didn’t enjoy the gambling.”

“She felt the danger, even at a remove,” Milch said.

At times, the memories came flooding back. “My dad was a big tipper,” Milch said. “He would take me down to the winner’s circle, carrying me.”

Recalling how he got more serious about gambling in high school, Milch said, “My old man tightened up the cashier to carry his bets. And I would have a little action on the side. There was so much action going on. At some level, I became an irritant because I was carrying all this stuff, and sometimes I would forget.”

Although he was quieter at other moments, Milch was attentive as Rita and Hallenborg exchanged stories. “Even when he was working at the office, David was keeping tabs on what was happening at the track,” Hallenborg said. “He would send people to the track to place his bets or pick up money. He would talk to the trainers.”

“Now I’m the wretched wretch you see before you,” Milch quipped, much to the delight of his tablemates.

Rita and Hallenborg were both stunned by Milch’s enthusiasm when they presented him with pages of the script. They said his sharpest talent, still, is shaping and editing screenplays.

“He’ll just start in on them,” Rita said. “I compare it to a musician playing an instrument. He just starts riffing. He can still bring the magic, even though he’ll forget or get disconnected.”

That disconnection is visible in one draft of “The Last Horsemen.” While making notes around lines of dialogue, Milch suddenly segued into composing a scene for “NYPD Blue,” which includes exchanges between Det. Andy Sipowicz (played in the series by Dennis Franz) and other characters from the ABC TV show, which ran from 1993 to 2005.

As “The Last Horsemen” script reached its final stages with Milch adding his notes, Rita had other contributions and insights on characters that significantly improved the story, Hallenborg said. After those additions, they thought maybe, just maybe, “The Last Horsemen” might have enough commercial appeal to be produced.

While the screenplay is shopped around, the focus of the unusual partnership has switched to an idea hatched by Hallenborg that he hopes will lead to a TV series. The story is inspired by two young men he met on social media — one who has been in recovery and another who has been in and out of prison.

“He’s a fascinating, talented, handsome, smart, charming sociopath,” said Hallenborg of the second man. “I’m 38 years sober, but prior to that I had plenty of association with people who were outlaws. This is not unfamiliar ground to me.”