For a cast this talented, the end result is disappointing

And one of the underlying themes - our ever-increasing reliance on technology - is very pertinent.

Writer-director Sam Esmail (Mr Robot) adapted Rumaan Aslam's book of the same title. The story begins in Brooklyn in New York City with a chunk of clumsy expository dialogue. Cynical, stressed adverting executive Amanda Sandfield (Julia Roberts) spontaneously books her family - college professor husband Clay (Ethan Hawke), who's more easygoing, and their teenage children Archie (Charlie Evans) and Rose (Farrah Mackenzie) - into a luxurious country house for a weekend getaway.

At first all seems great - there's a swimming pool to enjoy and the surroundings are beautiful - but in the middle of the night two strangers appear at the door, African-American G.H. Scott (Mahershala Ali) and his young adult daughter Ruth (Myha'la). G.H. says he's the owner of the house and, while acknowledging that the Sanfields have paid for their weekend, says they want to stay. Some kind of cyberattack has happened in the city and things aren't good there and will get worse.

The Sandfields are a bit taken aback by the sudden arrivals and the vague news of something bad. Since their mobile phones, computers and the TV are not working - giving some credence to the idea of a cyberattack - there's no easy way to find out more, although occasionally the devices come to life briefly to provide a little tidbit. At least the electricity still seems to be working.

Amanda, in particular, is suspicious and not a little racist (and Roberts commits to these unpleasant aspects of the character). Are these people who they say they are? Could they really afford such a place? Clay is more willing to let the Scotts stay and work things out the next day so, with some discomfiture on both sides, that's what happens.

The race and class issues keep recurring, perhaps exacerbated by the mysterious situation and ominous events.

This is one of those movies where information is doled out gradually and often cryptically and we're often left to put our own interpretations on what's happening as we know what the characters do.

There are some striking scenes. One involves a bunch of self-driving white cars sitting empty on a road, with more coming intermittently to crash into the others; in another, Kevin Bacon makes a brief but pointed appearance as a survivalist.

Sometimes the special effects seem ever so slightly off, perhaps because the scenes they're in are so incongruous - a large ship running aground on a beach; a herd of deer mysteriously congregating near the house - but for once the jarring effect seems to enhance rather than detract from the feeling of unease created.

Rose's thwarted desire to see the last episode of Friends (she'd been bingeing before the sudden trip) keeps coming up and becomes a little irritating: surely one of the others knew what happened and could have told her so they could get on with bigger things?

I didn't mind that not all the questions were answered or the characters and storylines accounted for but, given the lack of resolution, I wish the film hadn't taken quite so long to tell its story. Watching it in portions like a TV show - and it is divided into named sections - might be more satisfying.

There are rewards if you're patient but like the similarly themed M. Night Shyamalan film Knock at the Cabin, this was disappointing.