One of my favorite David Fincher movies (of which there are several) is Zodiac. What makes it work so well isn’t that it “solves” one of the most infamous cold cases in American history, but that it compellingly portrays how the obsession with trying to solve something that might not be solvable can ruin a person’s life. In the end, it becomes less a triumph of perseverance and grit than a pathetic throwing away of a life’s potential.

The four-episode documentary series The Most Dangerous Animal of All, adapted from a book of the same name, is an interesting companion piece to Zodiac, although I’d hesitate to call it perfect.

It’s about Gary Stewart, who was adopted as an infant into a loving family. For decades, he struggled with questions of his real identity and what it meant to be abandoned by his birth parents, so he started working to track them down. He found his birth mother easily enough and through her learned that his father was a guy named Earl Van Best, Jr.

Best was a bad dude at the time he met Stewart’s mother. And by “met” I really mean kidnapped, raped, and abused. He was 27 years old at the time, she was only 14. Their “love affair” even made headlines, allowing Stewart to get not just a feel for the circumstances of his birth but pictures and even some in-court film of his father when he was eventually caught, convicted, and sentenced for his crimes.

All that was bad enough, but then Stewart, armed with a mugshot of his father, saw a documentary on the Zodiac killer and that iconic drawing of the suspect:

Stewart realized it looked a lot like his father. This sets him off on an odyssey to determine whether his father was, in fact, Zodiac and solve this coldest of cold cases. Through the first three of the four episodes, Stewart marshals his evidence and it sounds pretty compelling. He wrote the book upon which the series was based and then, well, it all went to shit.

What’s particularly interesting is, according to this article, said going to shit started happening while this documentary was in production. This left the creators in a pickle – how to deal with the evidence that seemed to show that Stewart’s argument that Best was Zodiac was full of shit? The way they handled it was to present, point by point, experts debunking each of Stewart’s claims – to him. Essentially, they made the documentary on one track, all the while building the case against Best as the Zodiac (culminating in records showing he wasn’t even in the United States when the Zodiac killings took place) on another, only bringing them together in the end.

The result is compellingly awkward. You might expect that Stewart, confronted with the evidence contradicting his theory (some of which implies he just made shit up), that Stewart would come clean or break down in some way, blame the stress of his quest for driving him down this particular rabbit hole. Instead, he steadfastly holds onto his conclusion that his birth father – who had nothing to do with raising him – is the Zodiac killer.

To what end? It’s not clear. Maybe it’s because Stewart is so desperate for a personal history, an identity that latching onto one that horrible is preferable to not having one at all. Maybe it’s that, if he’s going to be the offspring of a monster, anyway (which Best, by all evidence, was), might as well be the offspring of one of the most infamous (and unidentified) monsters of all time? Or, maybe it was all a grift, with Stewart coming up with a slick way to monetize his search into his background.

I don’t think it’s the last one. From the documentary it really appears that Stewart believes the story he’s trying to sell. Either of the others are heart wrenching, in their own way, and make you feel sorry for him. Which is what makes this series so compelling – come for the potential true crime bombshell, stay for the fascinating portrait of a man who is so wrapped up in the distant past that he can’t come to grips with the more recent version.