Call Me Lucky starts out as a biopic of a comedian you’ve probably never heard of and ends up addressing another subject entirely. At first, it feels like unbalanced filmmaking, and director Bobcat Goldthwait probably should have introduced the crux of his documentary sooner. But the second half of the film is too compelling for viewers not to forgive the misstep.

Lucky telegraphs its sharp left turn miles before it takes it, but it sinks the stomach nonetheless. Until that point, we get to know Barry Crimmins, an abrasive Boston comic and Goldthwait mentor who looked like a portly, furious, chain-smoking Mr. Kotter back in the day.

But if you want descriptions, go to tape: The film kicks off with a long, wearisome parade of friends and colleagues offering a parade of adjectives and comparisons (i.e. “Noam Chomsky and [Popeye’s] Bluto”). We get quick clips of Crimmins onstage, always with a beer and cigarette while he bitches about the world with an anger far beyond most comedians’ bemused “what’s the deal with…” intros.

Crimmins founded two clubs in Boston and is credited with boosting the careers of the likes of Denis Leary, Steven Wright, Paula Poundstone, and Kevin Meaney. He was prescient, criticizing foreign policy and joking about the prospect of a cable network dedicated to war—“All War, All the Time”—in 1982. When Goldthwaite lets present-day Crimmins cut in, the now-gray-bearded man who lives on a large tract of land in the woods says he wants to leave his mark on the world in two ways: “I’d like to overthrow the government of the United States. And I’d like to close the Catholic Church.” Alrighty, then.

Goldthwaite’s not a director who shies away from uncomfortable subjects—2009’s fantastic World’s Greatest Dad is one of his darkest—and between Crimmins’ ranting against Catholicism and subjects in the film making vague comments like “When all that stuff happened to him…” and “There was something shady and weird about him,” it’s not difficult to guess the big reveal.

Crimmins bared his soul in an early ’90s stand-up performance whose alleged reverberations calls to mind Tig Notaro’s 2012 “cancer set,” in which she deals with a recent cancer diagnosis by opening with, “Hello, I have cancer.” Whereas Notaro’s set rocketed her out of obscurity after comedians like Louis C.K. lauded it, the aftermath of Crimmins’ act was a lot of shock, sympathy, and claims that “now everything makes sense.” Afterward, Crimmins became a full-time activist, exposing himself to variations of his childhood trauma in an effort to take down AOL, which turned a blind eye to chatrooms dedicated to criminal activity in the days of dial-up.

The hearing and Crimmins’ subsequent advocacy, both private and public, are gripping stuff—and then Goldthwaite buries viewers under descriptions again, ones that paint Crimmins as angelic while saccharine music plays. It doesn’t matter what his friends say or how many stringed instruments accompany them when they say it. You know you’ve just become acquainted with a profane, irritable saint.

Call Me Lucky opens today at the Angelika Pop-Up.