There is something to be said for a simple, direct thriller, unfettered by overplotting and needless complications beyond the ones which make the story so tense and unsettling in the first place. "The Ones Below," the directorial debut of David Farr (screenwriter of 2011's "Hanna"), is such a suspenser, foregoing darkness and shadows for troubling psychopathy happening in the light of day. Clémence Poésy (2008's "In Bruges") is quite good as Kate, a first-time mother-to-be whose friendship with new downstairs neighbors Theresa (Laura Birn) and Jon (David Morrissey) takes a terrible turn when a freak accident causes Theresa to miscarry her own unborn baby. Theresa and Jon do not mince words in blaming Kate and her beau, Justin (Stephen Campbell Moore), for the fatal occurrence, but after returning from a sojourn to deal with their grief and clear their minds they are quick to apologize for their behavior. A relationship slowly begins to rebuild between the couples, but, as Kate comes to discover, not all is as it seems for two marrieds who seem to be coveting Kate and Justin's newborn son.

"The Ones Below" is fairly standard in its A-to-Z trajectory—comparisons to 1990's "The Guardian" and 1992's "The Hand That Rocks the Cradle" are warranted—but it is an effective "...From Hell" potboiler all the same. While Kate's desire to continue being friendly with Theresa—even allowing her to babysit her child—strains credibility in light of the nasty verbal blows they come to following the accident, writer-director David Farr foregoes overt violence and to-the-death showdowns for a quietly encroaching wave of paranoia as Kate begins to suspect she and her baby are in serious danger. One wishes more layers could have been brought to the deceptively personable Theresa, but Laura Birn (2014's "A Walk Among the Tombstones") is chilling precisely because of her helpful, smiling façade. And, if the appropriately prickly ending arguably explains too much in lieu of its initial enigmatic suggestions, it still makes for a grimly stirring closer. "The Ones Below" cannot attest to having the most original of plots. It is an effective film, however, one that ever more tightens its compellingly diabolical grip.