Sam Esmail’s “Leave the World Behind” starts with this generation’s worst nightmare; the internet goes down. For anyone born in the years after Generation Z, there is nothing more terrifying than not being able to check social media or email, post on Instagram, complain about everything, cyberbully the less fortunate, or stream a favorite tv show. What is one to do if our handheld metallic Svengali cuts us off from our little world?

The problem reveals itself to be much more concerning, as satellites lose power, destroying all navigation systems in the United States. At the same time, animal migrations are being disrupted, anti-American pamphlets seemingly fall from the clouds, and a crippling sonic noise brings people to their knees. The country has fallen into bedlam.

Esmail adapts Rumaan Alam’s unnerving 2020 novel of the same name, keeping the urgency of Alam’s story by opening it up cinematically. The filmmaker shows us the very real effects of a technological meltdown, with oil tankers plowing into land as unsuspecting beach goers look on and planes crashing due to the loss of their nav systems. These moments are handled well. Esmail is a smart director (his work on the television series “Mr. Robot” is top notch) and doesn’t reach for spectacle. Instead of resorting to the sloppy CGI one finds in the empty films of Michael Bay and Roland Emmerich, the director wants his film to be suspenseful and unsettling, assuring his audience this is no bargain basement disaster flick. In equal measure, the director takes great care with the film’s visual stylings (courtesy of Esmail’s longtime cinematographer Tod Campbell) and its characters.

Giving the most human performance of her career, Julia Roberts is Amanda, a woman who dislikes her fellow mankind and lives in an upper-middle class Brooklyn neighborhood with husband Clay (the always reliable Ethan Hawke) and their two children, Archie (Charlie Evans) and Rose (Farrah Mackenzie). As Amanda, Roberts does terrific work. Nailing her character from the very first scene with the declaration, “I fucking hate people.”, the actress seamlessly traverses Amanda’s complexities. Although it is hinted that the couple’s marriage is now sexless, Amanda obviously loves her husband. She is giddy to have impulsively booked a week’s vacation for the family and cannot wait to leave the overcrowded city and its inhabitants.It is unclear if Amanda is happy to be alone with her clan or just happy to get out of New York. There are also hints of a drinking problem and definitely shades of bigotry. Roberts isn’t showy (as she is much too often) and creates a kind of calm meltdown, eventually endearing the audience to this unlikeable woman. This is a rigidly emotional turn from the Oscar winner that ranks amongst her best.

Things are going peacefully until the owner of the Airbnb, George “G.H.” Scott (Mahershala Ali, always one of our finest character actors) and his daughter Ruth (Myha’la Herrold), show up unexpectedly due to a citywide blackout that caused them to flee back to the home. As Amanda’s bigotry-fueled distrust causes immediate tension, the two families have no choice but to hunker down together and try to figure out how to survive.

This is where “Leave the World Behind” works best, as the screenplay digs into the themes of class and race. The subtexts of Amanda’s racism are carefully explored. Her lines are frank but