The town in “Quarry” is never named, but anyone who has driven through Blaenau Ffestiniog on a wet afternoon will recognize it: the gray terraces, the mountains of broken slate rising behind them like the spoil of some enormous argument. Rhian Ellis shot her second feature there over six weeks last winter, in Welsh and English, with a cast that is about half professional, and the result, which had its premiere at the Rome Film Festival on Saturday, is the best British film I have seen this year.

The story is simple to the point of austerity. A survey crew arrives to assess an abandoned quarry for a hydroelectric scheme. Among them is Elin, played by the newcomer Catrin Howells, who grew up in the town and left at 18. On the third day, the crew finds human remains in a flooded gallery. The police come. The town, which has been waiting 31 years for this, closes like a fist.

Ms. Ellis, 39, whose first film was a small, funny portrait of a Cardiff taxi driver, has made something much colder and more controlled here. The camera, operated by the Polish cinematographer Agnieszka Woźniak, rarely moves. Scenes play out in long takes in kitchens, chapels, and the cab of a pickup, and the dialogue, much of it in Welsh with subtitles, is sparse and oblique. Nobody explains anything. Elin’s mother, played with magnificent stillness by the veteran stage actress Gwenda Pryce, says perhaps 200 words in the entire film and is its center of gravity.

What the film is about, underneath the procedural surface, is how a community decides what it can afford to remember. The dead man, it emerges, was not a stranger. Nor was his death, exactly, a crime, or not one that the town could have reported without reporting itself. Ms. Ellis lets this out in fragments, through a chapel hymn, a photograph, a conversation in a car park that stops the moment a third person approaches, and she trusts the audience to assemble it.

The film is not without weaknesses. A subplot involving the hydroelectric company’s London lawyer is thinly drawn and feels imported from a more conventional thriller. The score, by the Welsh composer Osian Rhys, is occasionally too insistent for a film that is otherwise so confident in silence. And the running time, at 118 minutes, could lose 10.

But the final 20 minutes, in which Elin must choose between the truth and the town, are as good as anything in recent European cinema, and Ms. Howells, in her first screen role, carries them without a wasted gesture. At the festival screening, the audience of 1,100 did not applaud at the end for several seconds. Then it did not stop.

“Quarry” screens again at the Rome Film Festival on Wednesday and opens in Britain and Ireland on Nov. 20. In Welsh and English, with subtitles. Running time: 1 hour 58 minutes.