Deceptively titled and oddly mis-marketed as a horror movie, Trey Edward Shults’s second feature It Comes at Night, might much more appropriately be viewed as a ‘post-apocalyptic psychological family drama’.

I’m often loath to place a movie under a genre classification, because certain movies might straddle several genres and don’t easily fit into pigeonholes. However, if you go to see It Comes at Night expecting a conventional horror film, you will be disappointed... or perhaps you’ll be surprised.

Shults sets his film in a vacuum – a cataclysmic event has occurred, what this might have been remains a mystery, but a deadly, pustular contagion is one result. The virus may be in the air, as gas-masks are often worn as a precaution, but it is certainly contagious, and contaminated bodies are immediately burned.

There is no information as to where this virus came from, how civilization has been affected or what still remains. There are no amenities such as electricity or a water supply, there are no explanations via radio broadcasts or internet messages.

Living in an isolated, boarded-up fortress of a house in the middle of woods, is a father, Paul, (Joel Edgerton) an erstwhile history teacher who has learned to be a survivalist. His entire existence revolves around protecting his wife, Sarah (Carmen Ejogo), and their 17-year-old son, Travis (Kelvin Harrison Jr.). He goes by the motto, “You can’t trust anyone but family”. The family survives by sticking to rules and a strict routine, and, being American, they are armed at all times. They live a wary existence. Outsiders are not welcome.

When a desperate stranger named Will (Christopher Abbott) breaks into their house looking for water and provisions, the family’s paranoia compels them to knock him out and tie him to a tree.

When Will regains consciousness, he pleads that he is himself a man with a wife and 4-year-old son. He manages to convince Paul and Sarah that his family may be dying of thirst not too far away.  

The now-allied fathers rescue and drive Will’s wife Kim (Riley Keough) and son Andrew (Griffin Robert Faulkner) back to the house, and the two families come to an arrangement to live together amicably. Clearly, if they join forces they will be safer... or will they?

In It Comes at Night, indistinct voices are heard mumbling behind walls; muted shuffling occurs behind locked doors; eerie howls echo outside at night; the family guard-dog runs off into the woods in search of something - an atmosphere of intensifying dread pervades the whole film.

It’s never made clear exactly what does ‘come at night’. Certainly nothing that manifests itself in any obvious way. What appears to come is fear, paranoia, and nightmare.

17-year-old Travis is particularly prone to bad dreams, and they intensify when newcomers Will, Kim and Andrew arrive.  Hormonal adolescent stirrings begin to torment him as he becomes acutely aware that he is the only male without a partner and without prospect of one. He eavesdrops on the bedroom conversations of the young couple and begins to have discomforting dreams about pretty Kim.

Despite best intentions, allegiances begin to fray when paranoia again begins to infiltrate the household.

Director of photography Drew Daniels keeps things in the dark -  the film is infused with a perpetual gloom, punctuated by close-ups of frightened faces by lantern-light. Even in the daylight the surrounding woods appears shadowy and threatening.

Houston-born writer-director Trey Edward Shults (still only in his 20s) presented a tense debut in his low-budget psychological thriller Krisha (2016). In It Comes at Night, he has contrived a situation which exposes the frailty of human connections under extreme pressure and insecurity - where fear forces kindly people to make brutal decisions. He places a tight-knit family in a post-apocalyptic world, where hunger and thirst are constant threats but other, less defined perils, prove to be even more deadly.