When it comes to matters of monstrous kin, modern horror movies tend to turn on the “bad seed” angle, viewing demonic or killer children through the eyes of their feckless parents. But rarely do we see the opposite — an elder parent’s devolution into madness through the eyes of their adult brood. Enter “Relic,” the feature debut from Japanese-Australian filmmaker Natalie Erika James co-written by Christian White, which shows an 85-year-old matriarch’s descent into otherworldly insanity from the points of view of her daughter, Kay (Emily Mortimer), and granddaughter, Sam (Bella Heathcote).

It’s safe to say that James’ film now owns the corner on the market of horror movies about women watching their mothers come hideously undone. , landing on a final image that ranks among the most harrowing of contemporary horror.

Upon news of her mother Edna’s (Robyn Nevin) unexplained disappearance, Kay is summoned back to Edna’s dilapidating rural home,...