Peacock’s latest docuseries entertains the idea that the famed Zodiac Killer never existed. So, what does that say about the series of murders that occurred in Northern California during the late 1960s? Well, English professor and lover of Hawaiian shirts Thomas Horan believes there were multiple killers involved and the cryptic letterist wasn’t connected to them whatsoever. 

Released July 11, 2023, Myth of the Zodiac Killer equips filmmaker Andrew Nock (Unidentified with Demi Lovato) with the task of making sense of Horan’s theory. While at times the show ventures into “Is this an irresponsible conspiracy theory masquerading as a documentary?” territory, Nock keeps his project grounded by giving valuable screen time to criminology and law enforcement professionals who disagree with the theory.

In the first of two episodes, Horan insists “the Zodiac Killer is a fictional character, he is a literary invention,” and spends two hours breaking down his theory. At times, you might agree with him, but at other times, he sounds absolutely unhinged – especially in the moments where a San Francisco detective accuses Horan of making up facts as he goes. 

The Zodiac Killer is thought to have seven victims, five of whom are dead. But in his coded letters, which were mailed to regional newspapers, the supposed killer claimed to have killed a total of 37 people. To this day, the killer has never been found. Horan considers that, perhaps, the early letters were penned by the killer, but the rest weren’t. He also doesn’t think the killer committed the crimes he’s credited for due to a series of changing factors, which includes the location and modus operandi of the killings. Ultimately, he believes the letters were written and delivered by a copycat, and the crimes were committed by multiple killers. The documentary even welcomes a conversation with one of Horan’s suspects, who gives a bone-chilling performance when he whole-heartedly laughs after being asked if he killed the victim, and an alleged witness publicizes her experience for the first time ever.

Curious to go down Horan’s rabbit hole? Here’s everything you need to know about the amateur detective’s claims throughout the docuseries.

Horan firmly believes that the Zodiac Killer isn’t real and instead, multiple killers committed the crimes that the killer is credited for. Horan claims that the only evidence professionals use to connect all the murders to the same person were the letters that awarded the supposed killer his nickname. “There was no serial killer, there was no single killer involved in these murders and the person writing these letters didn’t commit any of the murders,” Horan boldly states within the first 10 minutes of the series.

Throughout the show, Horan brings forth his evidence, which is displayed in a chart that gives details about the victims, including the location of their murders, the weapon used to commit the crime, and how they met. He finds that the information is inconsistent. While he uses that as a main mode of evidence, it is dismissed by multiple professionals who state that many killers change course during their active period to perfect their attacks or to build adrenaline.

Another piece of so-called evidence is that there are two different drawings that have surfaced of the alleged killer, both of which were drawn up by professionals who spoke to witnesses of the crimes. One image shows a thin-faced man with glasses and short hair, whereas the other shows a man with a rounder face, no glasses, and a side part in his hair.

Additionally, the series makes time to hear from people who are crucial to Horan’s theory, including victim Darlene Elizabeth Ferrin’s ex-husband James Phillip Crabtree, who was a suspect at one point but was absolved after being interviewed. Towards the end of the first episode, Crabtree is asked if he committed the murder and he insists that he didn’t, but first he engages in a hearty laugh. Later, he calls Ferrin’s mother a “little bitch” for suspecting him as the murderer. After his recount, Nock and Horan accuse him of telling multiple small lies.

Another person interviewed is Linda Jensen, who claims that she was a witness to the attack of Bryan Calvin Hartnell and Cecelia Ann Shepard at Lake Berryessa, which resulted in Shepard’s death. Jensen claims that she was at the park moments before the attack and, along with her friends, was being stalked by a man who was hiding behind a tree. After the group lost track of the man, they rushed to their car in fear. Her account of the killer matched Hartnell’s description, given that he survived the attack, which dismisses the drawing of the killer that was conceived after a later murder.

Horan insists that the person who wrote the Zodiac letters isn’t connected to the murders, due to their inconsistencies. The first letters signed by the killer were delivered in 1969 after the first two murders and before the Lake Berryessa attack. Three letters were allegedly sent by the killer to three different local newspapers, and they had striking similarities. Following the attack at the lake, no more letters were received until the murder of the lone cab driver Paul Stein, and then they allegedly continued until 1974, totaling in 28 new letters.

“It’s these 28 [letters] that Professor Horan have an issue with,” Nock narrates in the series. Horan jumps in, stating, “In my opinion, the only really authentic Zodiac letters are the first three letters that were mailed to the papers with the code, then immediately there was a follow up letter. After that, there were serious doubts.”

Nock summarizes, “So, Professor Horan believes that the first four letters that arrived after the so-called second Zodiac murder could be legitimate, but the remaining 28 that arrived after the alleged Paul Stein murders are not.” Nock sends the letters to linguistic experts, who found that the letters, by themselves, lack in sufficient evidence to support either side.

The most admirable aspect of The Myth of the Zodiac Killer is that it doesn’t allow Horan to get away with any misspeaking or ludicrous claims. Throughout the two episodes, his claims are consistently countered by a group of professionals, regardless if Nock feels there is validity to his statements. As Horan suggests new suspects, the officers explain why they were absolved of the crimes, but in the final act of the series, the aforementioned linguistic experts claim there’s a “likely change” in the style of the letters before and after the Paul Stein murder that indicates the possibility of a second person writing them.

“The phenomena that we observed here are clear enough to, at least, raise doubts,” the expert says. However, the criminology and law enforcement professionals claim that this could just be due to a fear of being caught. “The notion that there was a change in the writing after the Paul Stein murder could indicate that there was more than one person involved, but I think it could also be a psychological shift in the killer himself,” said one professional. Another discredits Horan’s theory entirely, calling it “speculation by an armchair detective.”

In all, the series doesn’t do much to give weight to Horan’s claims or raise any substantial questions, and in its final moments, it focuses on the “real tragedy” of the murders. Horan says, “The real tragedy of the myth of the Zodiac Killer is not just that it robbed the victims and their families of justice, and that it robbed society of justice. People have become so wedded to their beliefs that they hold onto them, even in the face of clear, contradictory evidence.” And while that observation is right, in the general scheme of things, we aren’t convinced that it makes much sense when applied to this unsolved case.

The Myth of the Zodiac Killer is currently streaming on Peacock.