Escaping their abusive father in England, a young family using the name Marrowbone relocates to America, to start their lives afresh in the mother's isolated childhood home - which has been unoccupied for 30 years.
Soon after arriving, the children - Jack (George MacKay), Billy (Stranger Things' Charlie Heaton), Jane (Mia Goth), and Sam (Matthew Stagg) - meet Allie (Anya Taylor-Joy), who lives on a neighbouring farm, and a firm friendship is forged over the summer.
Unfortunately, after the summer, the mother falls ill, and having told the children to stay secluded until Jack turns 21 (to avoid being separated by the authorities), she dies.
The Marrowbone family cuts itself off from the nearby town, and Jack now only gets to see Allie infrequently, when he leaves the home to buy supplies or to steal precious moments with his beloved.
However, the family's skeevy lawyer, Tom Porter (Kyle Soller), who also has the hots for Allie, senses something is afoot at the Marrowbone house and, driven by his desire to woo Allie (despite her making it clear he's barking up the wrong tree), pries into the mysterious family's life... with disastrous consequences.
Having failed to make it to the cinema at the weekend to get my required dose of Anya Taylor-Joy goodness in Glass, I turned to this seemingly overlooked psychological horror-cum-family drama from the other year.
Thematically it reminded me strongly of Ian McEwan's 1978 novel The Cement Garden - which has had a lasting impact on me since I read it about three decades ago - with its similar focus on an adultless family living in hyperreal isolation, with elements of Psycho and Lovecraftian horror (but not the cosmic monsters and weird cults kind) mixed in for good measure.
Although set in the late '60s (the 1969 Moon landing is being shown on a TV in a store in town), the Marrowbone kids are carving out a very Waltons-esque existence of tatty dungarees and Spartan living conditions.
For two-thirds of the movie, Marrowbone feels like an enormous Gothic tease, eschewing jump-scares entirely in favour of continually heightening its atmosphere and tension, building - seemingly - to a climax that never comes, suggesting ghosts and weirdness when none are truly evident.
That is, until the plot twists unravel thick and fast at the turning point that throws us headlong into the final act.
To be honest, if you've watched enough movies in your life, the revelations aren't that original, which is probably why this film hasn't received the interest it perhaps deserves.
However, they are handled deftly by writer/director Sergio G Sánchez, who brings out top-notch performances from all of his cast.
As with many clever films, once you know the "secret" of Marrowbone there's a strong urge to watch the film again to see how it all works.
And that can't be a bad thing.