“There’s a primal wound that adoptees have,” proclaims memoirist Gary Stewart at the start of the documentary The Most Dangerous Animal of All. “If you weren’t loved enough to be kept, how can you expect someone else to love you?” This self-mythologization via self-pity is the approach that Stewart takes to presenting his near-fantastical claim: that he believes his father to be the Zodiac Killer.
The identity of the Zodiac Killer, who murdered five victims in the late 1960s and early 1970s while taunting the San Francisco police and populace through the media (as recounted in David Fincher’s 2007 film Zodiac), has long been a true-crime holy grail. Perhaps unsurprisingly, Stewart received significant blowback from “Zodiac-ologists” when he published his theory in a 2014 best-seller (co-authored by Susan Mustafa). Still, he has been steadfast that he, and he alone, has solved a mystery that has eluded decades of official and amateur sleuths.
Thankfully, The Most Dangerous Animal of All — the first in FX’s docuseries slate — is hardly a credulous retelling of Stewart’s story. Director Kief Davidson allows the author to have his say and add new evidence that he’s uncovered since the book’s publication, but his team also does what Stewart’s publisher, Harper Collins, apparently never did: fact-check his assertions. (To be fair, a fact-checked nonfiction book is an anomaly; writers bear the responsibility to commit the truth to paper.) It’s in those verifications that the documentary justifies its existence (though it never justifies its four-hour run time, which is stuffed with corny close-ups and re-creations).