Following years away, twins Eli (Nick Stahl) and Mary (Kelli Garner) along with younger brother Tommy (Scott Haze) are forced to confront the horrors of their childhood, and the buried secret that binds them, when they are all drawn back to the family farm. And it is likely you may never see a more dysfunctional family than the one at the centre of Vincent Grashaw’s Southern Gothic drama What Josiah Saw.

To say Grashaw’s film is a slow burner would be to understate somewhat. It is ponderously paced at times, the final act a reward for perseverance as much as is a disturbing resolution to the story. Yet What Josiah Saw is never less than engaging, the siblings’ current lives playing out as if a kind of purgatory for the as yet unknown events of their youth. Split into four chapters the contrasting stories are laid out, and while secrets are inferred, you’re never quite up to speed, Grashaw’s considered direction of a well-crafted script maintains a wary distance.

The performances add to the aura of unease. Robert Patrick is carving out something of a niche as an oppressive patriarch, retaining a hold over his children even as they grow into adults and Stahl and Haze balance their characters delicately on a line over which insanity likely awaits. It is Garner who impresses most, however, inhabiting a character permanently in distress, ever on the verge of emotional breakdown.

While perhaps requiring a tighter edit, What Josiah Saw is nevertheless an effectively unsettling, often uncomfortable watch, and the tense, shocking finale will linger long after the film is over.

What Josiah Saw streams on Shudder from August 4th,