A man believes his dad is the Zodiac Killer in this trailer for FX's first true crime docuseries

There’s no shortage of films and documentaries unpacking the enigma of the Zodiac, the still-unidentified serial killer who plagued Northern California in the late ‘60s and early ‘70s. But what separates The Most Dangerous Animal of All from the rest is Gary L. Stewart, whose investigation is informed by blood—he believes the Zodiac Killer is the father who abandoned him as a child. (Stewart, we should note, is not the son of either Ted Cruz or John Carroll Lynch.)

The four-part true crime docuseries, FX’s first, is based on Stewart’s New York Times bestseller, which he co-wrote with author Susan Mustafa. As the below trailer demonstrates, Stewart has ample evidence to support his claim, but the complex bond he shares with the man he considers the Zodiac no doubt colors his findings, as well as his own identity. “It’s been consuming his entire life,” one voice asserts.

The Most Dangerous Animal of All premieres in its entirety on March 6.