Many Telluride Film Festival attendees prioritized, in the first days of this year’s fest, screenings of high-profile titles that already have distributors. But by Monday, more of them — us — were able to branch out a little bit and catch up on lesser-known titles that don’t yet have a backer. One such film, the fest’s second screening of which just let out at the Werner Herzog Theatre, is called September 5. (It had its world premiere at the Venice Film Festival last Thursday and its North American premiere here last Saturday, shortly after which its relevance and timeliness was reinforced by tragic real-world events.) And here’s the kicker: it might be the strongest narrative film of the entire fest! It certainly left many festivalgoers — industry insiders and civilians — absolutely buzzing as they left the venue.

If/when this 94-minute flick — the story of ABC Sports’ coverage of the...