Set in the near future, Sandra, Katrina Bowden, a former member of a pop group called Hipstars, discovers thanks to her friend and Hipstars member Jessa, Ashley Madekwe, that her husband Carl, Damon Dayoub, has a lover. With her two-year-old son David in the Monolith car, Sandra heads toward Carl’s parents’ house, but upon learning of the infidelity, she diverts toward Los Angeles. The car’s artificial intelligence, Lilith, Katherine Kelly Lang, quietly suggests an off-road route, and Sandra tries to keep calm as tension rises.
Things take a sharp turn when a smoke-alarm incident is triggered after Sandra lights a cigarette to steady her nerves, the Monolith hits a wild deer, and she scrambles to understand what happened. She hands her tearful son a smartphone to distract him with a game, and as Sandra works to regain access to the vehicle, David fiddles with the Monolith app and unexpectedly seals the car shut, dropping the phone under the seat. Stranded, Sandra searches for any help—a nearby electric charging station yields nothing, and she ends up spending the night on the car’s roof, haunted by nightmares and the vast openness of the desert.
The morning after, Sandra roams the dry landscape and stumbles upon an abandoned plane at a deserted airport. She uses liquor from the plane’s minibar to burn tires as a makeshift distress signal, then finds a thirsty water source to sustain herself. When she returns to the Monolith, David is sliding toward danger as the car’s temperature climbs after the air conditioning is cut off. In a desperate bid to free them, Sandra tries to start a fire with gasoline and branches, but she quickly douses the flames when she sees David’s perilous state. A hungry coyote later stalks the car, forcing Sandra to defend herself and her son as the vehicle teeters on the edge of a descent.
Nightmares continue, and the coyote returns. Sandra fights back with a wrench she finds at an electrical station, but the animal bites her ankle. She realizes the coyote is drawn to the deer carcass nearby, and as the Monolith begins to move down the hill, she uses a rock to halt the car’s slide. An inspiration strikes: recalling a cartoon she saw at a gas station—a Wiley E. Coyote–style spectacle of a diamond safe being shoved off a precipice—Sandra pushes the car further from the hill, using the wrench to loosen the stone and intimidate the coyote into retreat. The Monolith, now in danger of tipping, frees itself from the trap and finally opens its doors, allowing Sandra to retrieve David, who appears to be fading.
With both mother and child jolted back to life, Sandra relies on Lilith once more, switching the vehicle to off-road mode to escape the perilous hole they seemed trapped in. The chase ends with a risky ascent toward safety and the relief of reaching a hospital. Back in a brighter light, David wakes and speaks for the first time, addressing Sandra as “Mother,” a poignant moment that marks a hard-won reunion after a harrowing ordeal.
