Not a nadir in recent horror cinema, but well below average — and sea level — “The Cellar” is a logy contraption whose basic elements seem all too obviously determined by international co-production requirements, rather than any internal logic. Toplining scream queen Elisha Cuthbert as a mother who unwittingly moves her family into a house of supernatural peril, this West Ireland-shot thriller, made in conjunction with Belgian interests, is technically polished. But writer-director Brendan Muldowney’s latest lacks the thick atmospherics that might have punched across a sketchy screenplay, which falls short in expanding the premise of his 2004 short “The Ten Steps.” RLJE Films is releasing this SXSW premiere to North American theaters on April 15, simultaneous with its streaming launch on Shudder.

Muldowney’s ten-minute short is basically recycled as a first act here, with a tad more setup. Married advertising professionals Keira (Cuthbert) and Brian (Eoin Macken) have moved to a rambling old manse in the Emerald Isle countryside for the sake of work. Which doesn’t make much sense, any more than Dad sharing an Irish accent with grade-school son Stevie (Dylan Fitzmaurice-Brady), while Mom and sullen teenage daughter Ellie (Abby Fitz) sound pure Yank. Nevertheless, the family’s principal issue is initially dealing with said teen’s bad attitude, which apparently predated the move she’s now very unhappy about. Left alone to babysit Stevie while the parents have a business dinner, an already-spooked Ellie finds the lights going out. Instructed by phone to go downstairs and find the circuit breakers, she descends into the dank cellar… and disappears.

Police assume she’s a runaway, but Keira believes something else is going on. Her research into the house’s puzzling past excavates a tangle of ominous gobbledygook encompassing 12th-century alchemists, Knights Templar, Schrodinger’s Cat, mathematical equations, and a Biblical sea monster, all somehow adding up to that generic menace “an ancient evil.” This evil wants this family — but what for, or why, “The Cellar” doesn’t bother explaining.

Even such rudimentary “demon bad, family good” dynamics might pass muster if the undercooked narrative were flavored with enough creepiness in mood and setpieces. But aside from a few adequate jump scares, the film stubbornly refuses to develop any suspenseful grip. There are far too many scenes (particularly burdened on Cuthbert) in which characters over-act fear while practically nothing is happening at all, even as Stephen McKeon’s original score labors to suggest otherwise, complete with “Omen”-like quasi-Gregorian chants. Even a climactic leap into fantastical imagery somehow comes off as lacking energy and imagination, like much else here: Hell appears to be an endless queue of somnambulists.

Worse still, it turns out the thin story’s terror trump card is having people recite numbers aloud as they count steps down to the cellar and/or a mysterious other dimension. This device is only moderately shiver-producing the first time. By the third or fourth, it’s a somewhat laughable reminder of the film’s inability to raise a fright, or even engineer basic suspension of disbelief. Meant to induce dread, hearing “1, 2, 3, 4…” instead becomes this lethargic chiller’s hypnosis-like call for the weary viewer to nod off.

An uneven cast manages to be unconvincing in different ways, their performance modes ranging from histrionic to uncommitted. Sometimes the leads barely seem to be in the same movie, let alone the same fictive family. It’s a pity, since “The Cellar” has the external materials needed for a spooky good time: The real-life historic home utilized as the primary location is impressive, and the surrounding scenic splendors are handsomely shot by DP Tom Comerford. Last year another Irish horror, Damian McCarthy’s “Caveat,” eked an ingeniously skin-crawling experience out of a cottage’s few dingy rooms, but this film can’t seem to find its own pulse — or raise ours — in a comparatively deluxe setting perfect for Gothic frisson.