In the annals of horrific Hollywood-related crimes that have left a lasting imprint on Los Angeles, the 1969 Tate-LaBianca murders have always ranked in the top tier. The bloody killing of pregnant actor Sharon Tate and others over two days by members of a cult headed by Charles Manson has sparked its own cottage industry of books and films, including Quentin Taratino’s “Once Upon A Time … In Hollywood.’

But acclaimed novelist and former Times reporter Michael Connelly has always been fascinated by another dark and savage incident, fueled by sex and drugs, which he says left a deeper scar on Hollywood and L.A. culture — the 1981 Wonderland Massacre, in which four people were brutally slain inside a posh home in Laurel Canyon.

Adult film star John C. Holmes, drug kingpin Eddie Nash, famed entertainer Liberace and his “boy toy” Scott Thorson were among the colorful personalities caught up in the case. A juror was bribed. Even after three trials, there were no convictions, and the killers were never brought to justice, making the Wonderland murders one of the LAPD’s most infamous cold cases.

The details, Connelly contends, were outrageous even by Hollywood standards: “There’s aspects of this story that I don’t think would work in fiction because you actually have to be more believable in fiction.”

After decades of writing bestsellers — many of them featuring the fictional, no-nonsense Los Angeles Police Department Det. Hieronymus “Harry” Bosch — and adapting his novels into popular series (Prime Video’s “Bosch,” Netflix’s “The Lincoln Lawyer”), Connelly is finally taking a deep dive into his obsession with the blood-soaked slaughter in MGM+’s “The Wonderland Massacre & The Secret History of Hollywood.”

With the four-part docuseries, which concludes Sunday at 10 p.m. and will be available to stream in full, Connelly, partnering with documentary filmmaker Alison Ellwood (“Laurel Canyon,” “The Go-Gos”), extends his exploration into the case, which started with his 2021 Audible podcast. The project also probes Hollywood’s decadent culture of nightclubs and underground parties during the 1970s and ‘80s.

A centerpiece of the project is an extensive interview with Thorson, who was portrayed by Matt Damon in the HBO film “Behind the Candelabra” — his memoir of the same name served as the basis. An addict who operated in Hollywood’s dark circles, Thorson served as key witness in the Wonderland case. Thorson died in August of cancer and heart disease.

Scott Thorson, who died in August, was a key witness in the Wonderland case.

(MGM+)

The first chapter of the series, “The Heat of a Cold Case,” outlines the gruesome discovery on July 1, 1981, of four people — Ron Launius, William “Billy” Deverell, Joy Miller and Barbara Richardson — who had been bludgeoned to death. The victims were members of the Wonderland Gang, a group of small-time drug dealers. Launius’ wife, Susan, survived the attack but suffered brain damage and partial paralysis.

The slayings were allegedly ordered by Nash as retaliation for a robbery at his home, but Nash and his bodyguard, Gregory DeWitt Diles, were acquitted of the crime.

In a video interview, edited here for length and clarity, Connelly and Ellwood discussed the effect of the Wonderland case on Hollywood, its connection to the crack epidemic, the cat-and-mouse interactions with Thorson and whether there’s a possibility of reopening the case.

Why have the Wonderland murders intrigued you more than the Manson family murders?

Connelly: They’re both brutal, very shocking crimes. They both have something to say about the culture of their time. But Wonderland was on the precipice of huge change in terms of drugs being much of the inspiration and cultural change. It was the shifting to drugs that were designed to addict. That headed toward crack, which destroyed communities. So the impact was much more significant than the Manson case. Its tentacles go all over the place. It’s not only Los Angeles but representative of what happened in our society in the ‘80s.

Ellwood: When Michael first approached me, I had just finished “Laurel Canyon,” about the music scene there. The Manson murders marked the midpoint of that, this dark wave that no one was suspecting in this bucolic place. It had been mind-expanding drugs before, and then the drugs turned to cocaine. The artists leave, and then these houses become drug dens occupied by thieves. The image of what Laurel Canyon had been was taken over.

Michael, when did you first start obsessing over this murder?

Connelly: I first came to Los Angeles from Florida in the mid-’80s to cover crime for the Los Angeles Times. Any kind of story where people got away with murder was intriguing to me as a journalist. Then I transitioned to novels, and what happens in novels? Everything gets solved, there’s no loose ends. The opportunity to explore this case where justice was never served is something that intrigues and obsesses me. Over time, I’ve come to know almost every detective who has worked on this case. It has really stuck in their craws and that kind of transferred to me.

One of the most shocking images is the bloody footage from the actual crime scene.

Ellwood: It’s really brutal. I watch a lot of movies, so I’m used to gore. But when it’s real, it’s very different. There is much worse imagery, which we did not use.

How is the docuseries different from the podcast?

Connelly: It’s a visual story. The archival stuff that Allison and her team were able to pull together took it several steps above a podcast. The footage from the crime scene alone is significantly different when you see it. We got fresher interviews.

Michael Connelly and Alison Ellwood took a noir approach to shooting the docuseries.

(MGM+)

What was the main element to make it into a film?

Ellwood: The story struck me as a very negative image of what L.A. had become during this era, so we really wanted to take a noir approach. We have a lot of night driving with Michael, and very moody settings for the interviews.

The Zoom interviews that Mike was doing with Scott Thorson were immediately intriguing. You could see this back-and-forth, cat-and-mouse game that Michael was having to play with Scott. I thought, “Wow, we got to get them in a room together.” So we went to Musso and Frank’s in Hollywood, a luxury, old-time environment. Scott had hung out there a lot.

Connelly: He’s such a strange and interesting character. All these cops counseled me: “You got to watch him, don’t trust anything he says.” I went from being very standoffish about him and not trusting him to really enjoying our conversations. It was an interesting relationship. He was such an interesting foil who I would try to catch in a lie. Believe me, I tried. I thought it would be helpful if I showed him to be an unreliable narrator. I never told him where I lived, never gave him my cellphone number. But I ended up kind of liking him, despite all the bad things he did. And that’s a very strange thing for me. We knew he was sick when he did the interviews, but it was still shocking when he passed.

Is there a possibility of the case ever being reopened?

Connelly: Yes and no. Our work on this project got the head of the cold case unit of the LAPD to come in with the file and talk to us. But she basically said the case doesn’t have the things that would usually bring about a cold-case investigation decades later, like DNA and fingerprints. Someone would have to come forward to start this again.

Ellwoood: Certainly all of the detectives would be happy to bring this case to closure. It really is unrequited justice. People got away with murder.