Though it released in rolling fashion earlier in August, the gripping, emotionally devastating Sundance-minted documentary The Cove merits autumnal mention here because of the special timeliness of its narrative — the dolphin slaughter that it places under the microscope takes place annually in September.

Directed by National Geographic photographer Louie Psihoyos, The Cove tells the amazing true story of how Psihoyos, former Flipper trainer turned activist Richard O’Barry and an elite team of eco-warriors, filmmakers and free-divers embark on a covert mission to penetrate a tightly guarded fishing cove in Taiji, Japan. There, while being harassed by both local government officials and fishermen none too happy with the prospect of negative publicity, the Cove team shines a light on a dark and deadly secret that involves the capture and sale of thousands of dolphins, the annual slaughter of 23,000 more, the bureaucratic intrigue of industrial whaling international vote-trading, and mislabeled, mercury-spiked dolphin meat (beware, Jeremy Piven!) being packaged as part of compulsory Japanese elementary school lunches.

While it blends heartfelt reminiscences from O’Barry with a handful of interviews of people who will actually speak on camera, The Cove is, truth be told, mostly pieced together like a Steven Soderbergh heist flick, not some staid non-fiction film. Proving that some good actually came of the steaming pile of excrement that was Evan Almighty, the filmmakers tap one of that movie’s prop masters to help construct fake, hollowed-out rocks to house cameras. In clandestine fashion, the team then hides the cameras, along with underwater microphones, to capture the brutal carnage.

Psihoyos and editor Geoffrey Richman take a page from James Marsh’s Man on Wire, wringing drama from a foregrounded event; the bloody end result, even though you “know” what’s coming, packs more of a queasy punch than a dozen prefabricated Hollywood thrillers. The Cove is definitely, unapologetically subjective — a piece of social activist cinema all the way, complete with the call-to-action of David Bowie’s “Heroes” blasting over the end credits — but it’s also truly heartbreaking. You won’t feel good about feeling so wrapped up in the movie, sure to be short-listed for Academy Award documentary consideration, but you will feel. That much is certain. For more information, click here. (Roadside Attractions, 91 minutes, PG-13)