“Tone” is the triumph of the Welsh thriller “The Feast.” Tone — in its lonely, remote setting, its chilly, unsettling characters and the deeply unpleasant things that transpire — is everything.

The Welsh language (with subtitles) tale may take some getting used to, and the finale go absurdly overboard in “explaining” it all. Mystery is far spookier, after all. “Motives” don’t have to be underlined or punched out in bold type.

But veteran British TV director Lee Haven Jones does a swell job of knocking us off balance, and keeping us there in this disturbing story of dinner party horror in an Architectural Digest showplace home in the Welsh countryside.

Cadi, a poker-faced and largely silent pub waitress brought in as replacement kitchen/serving help by the lady of the house (Nia Roberts), stands out in an instant, even in this house full of characters on the creeper spectrum. Cadi is given a gawky, ungainly and faintly sinister air by Annes Elwy, and long before we see proof, we know something about that girl isn’t right.

Nervous, highly-strung and put-out wife and mother Glenda (Roberts) is almost normal by the standards of the family surrounding her.

Businessman/hunter Gwyn (Julian Lewis Jones) likes to keep up the illusion that he’s a man’s man, providing hares for the evening’s repast. But he didn’t shoot them. He found them strung up like an offering. Not that he tells anybody this.

Wrapped-too-tight son Guto (Steffan Cennydd) is an almost antic fidget, given to practicing his electric guitar on the lawn, plainly stir crazy about his surroundings. Whatever he uses to take the edge off is not available to him here.

“You can return to London when you’ve shown us you’ve grown up.”

And it’s too-apt that sometime med-student taking a break to be a triathlete Gweirydd (Sion Alun Davies) has a name that sounds like a Welsh version of “weirdo.” He loves his unitard and his body so much he can’t look away from the mirror or keep his hands off himself. He has one look, and it’s a leer.

Cadi? She freaks out at the sound of the hunter’s shotgun, is revolted by the sight of bloody carcasses and starts spit-cleaning the glassware for the night’s “make a good impression” dinner.

Something — many things — tell us she’s not up to the job. But the guests — business manager Euros (Rhodri Meilir) and neighboring farmer Mair (Lisa Palfrey) soon show up. Let the frazzled festivities begin.

Let’s just say nobody wants to take too hard a look at what’s going down in the kitchen.

Screenwriter Roger Williams, who has many Welsh and English-speaking TV credits, serves up sibling rivalry and accidents, ancient lore in collision with modern, money-grubbing short-sightedness — all stirred into a sometimes revolting stew of conflict cooked up by the off-center and off-putting Cadi.

We can see, in a larger sense, where this is going. But the waypoints and jolts in the many titled chapters (“I Want to Make a Good Impression,” “There’s a feast awaiting us,” etc.) that play out here are largely unexpected.

The gore of the third act has been mysteriously foreshadowed in the opening image. And yet Williams and director Jones feel the need to lay it all out there in subtitled explanation, dispelling what mystery there is about the film.

The “surprise twist” is a little surprising, but it tends to break the “What the hell is she on about?” mood of the piece.

And as mood encompasses tone, the behind-the-camera folks thus almost let down the confused, endangered and overmatched characters and the actors who play them in front of it. Almost.

Rating: unrated, graphic violence, sex

Cast: Annes Elwy, Nia Roberts, Julian Lewis Jones, Steffan Cennydd, Sion Alun Davies, Lisa Palfrey and Rhodri Meilir

Credits: Directed by Lee Haven Jones, scripted by Roger Williams. An IFC Midnight release.

Running time: 1:33