In a hospital in Seattle, Samantha and Will learn that their baby will be a boy. Later before leaving for the airport, Will tells Samantha that he’ll ask her father for permission to marry her. In Chicago, Will goes through some business meetings before visiting Samantha’s parents Paula and Tom.
They receive him into their home but the mood is clearly very tense. During dinner, Tom explains that he’s heard that Will and Samantha are thinking of getting a place together and asks for assurance that if the couple ever splits up, Will won’t claim any money Tom sent to help his daughter. Will tells him he has a good job and they don’t need his money, triggering an argument.
Paula tries her best to calm the men down to no avail, so in the end she comments that it’s getting late to make Will leave before things escalate. The next morning Will is awakened by a video call from Samantha and realizes he’s late for his flight. She wants to discuss what happened with her parents, but the call is interrupted by lots of strange noises.
Samantha explains that the power has gone out and says something is wrong, even admitting she’s scared. The screen starts failing and the call ends. Will tries contacting her again to no avail.
On his way to the airport, Will keeps on calling but Samantha never picks up. When he tries to board his plane, he’s surprised to discover that all flights have been canceled. On the news, they talk about huge seismic events off the Southern Californian coast until they lose contact with their LA studio.
A report arrives announcing power and telecommunication outages across the western part of the country. Suddenly the screens start failing and power goes out in the airport as well. Will leaves the building and notices people panicking everywhere, so he pays a taxi driver extra money to take him back to the city.
On the way, Will tries to keep calling Samantha but there’s still nothing. Moments later he returns to Paula’s place and has to take the stairs because the elevator isn’t working. He tells Samantha’s parents about his last talk with her while noticing fighter planes flying above the city.
The couple is packing and Tom explains he’ll go pick up Samantha while Paula goes to their son’s house, so Will agrees to go with him. Once they reach the street, the car gets stuck in terrible traffic as most citizens are trying to get away. GPS and cell services aren’t working and people are storming stores to get food and fuel.
The duo stops at a supermarket and Tom goes inside for supplies while Will fills up a gas tank. A woman approaches him to flirt and when he turns her down, her friends come to her defense. When they’re about to break the car windows, Tom yells at them to stop.
He pretends he’ll give them some money but when he gets to his car, he takes out a gun and points it at them until they walk away. While the duo drives away, Will complains because Tom didn’t tell him he has a gun and Tom reminds him that they didn’t lose their things thanks to it. At the highway, the traffic jam is even worse and the army is blocking the way.
Tom comes out to talk to the soldiers and explains his situation until they take pity on him and let him pass. Moments later they see that the trains are heading west with lots of army equipment, which makes them more worried about what may be happening. In the evening a police car makes them pull over.
Will gets out to speak to the officer but Tom immediately realises that it’s not a real cop and yells at his friend to come back. When the stranger tries to open fire, Tom drives the car in reverse to scare him off and ends up hitting the police vehicle. Then Will quickly gets back in the car and they drive away as the fake cop fails to shoot them.
Since the stranger is coming after them in the police car, Tom tells Will to load his gun. Suddenly the fake cop hits their car from behind and Tom has to take a moment to regain control of the wheel. When the guy starts driving next to them, Will fails to shoot him, and Tom has to explain how to load the gun correctly.
The cars continue to bump into each other as Will finally opens fire to no avail. Noticing an abandoned car by the road, Tom drives near it and forces the fake cop to crash against it to finally lose him. Moments later some deer appear in the middle of the road and Tom has to make a sudden turn, causing his car to go down the hill and crash against a tree.
This allows the fake cop to catch up and he points his gun at Will, asking him to come out. However Tom surprises him from behind and repeatedly hits him until he passes out. Then he informs Will that he broke his ribs.
Afterward the duo gets in the police car and uses it to tow Tom’s. The next day they arrive at a trailer park, where all the locals are wary of them. At the repair shop they meet Ricki, who agrees to fix their car.
On the radio, reporters explain that all communications are down except for local ham radios and short waves. The government has gone silent and nobody knows what’s happening. As cries for help mix with the news report, they notice the birds flying in strange patterns in the sky.
When Tom goes to the bathroom, he looks at the big bruise on his body, which hurts quite badly. Then Ricki tells him that she can give the car a temporary fix but it'll break again in the middle of the trip. Hearing that she was planning to leave for California, Tom offers her a deal: he’ll pay her to come with them, that way she gets closer to her destiny and can fix the car again whenever it breaks down.
After some hesitation, Ricki agrees by asking for more money. Before leaving they load the car up with Ricki’s tools. In the evening they notice that a car is behind them, so they pull over and turn off the lights.
After the car passes by, they drive after it by using their taillights as a guide. When Ricki checks her compass, she notices that the needle is spinning wildly. Suddenly another car appears on their side of the road, so Will has to quickly dodge and the new vehicle crashes against the one they’ve been following, sending them both off the road.
Will checks on one of the cars but finds no survivors. Ricki checks the other one and finds a dead woman. Her husband is trying to say something but can’t because he’s clearly on the verge of death.
When Ricki and Will say they should take him to a hospital Tom refuses, pointing out it’s too far and the man will just die mid-trip. Tom and Will get back in the car but Ricki is still stuck staring at the bodies. Soon another vehicle stops nearby and some creepy-looking men come out.
A wary Tom starts speeding up to escape but Will convinces him to pick up Ricki before they leave. As they take off, Tom explains he only picked her up because Will asked him to. Ricki is offended and says she won’t fix the car again, so Tom shakes the car to make her hit her face on the front seat.
Later when they stop the car to fill the tank, Ricki and Will watch the clouds behaving rather oddly. Suddenly lightning hits a utility pole and a huge storm begins. Tom has trouble driving because even with the lights it’s hard to see, so they decide to wait under a bridge until the rain stops.
The next day the trip continues under better weather. When they drive by a radio tower, the car radio picks up the signal. The reporter says there’s still no internet, no cell service, and no news from the government.
A few miles ahead, the trio finds the road blocked by the locals and their vehicles. The sheriff is wary of them but lets them pass when Will tells him the names of all the people he knows in this town. Afterward Will stops to visit his friend Meg, who shares that she hasn’t heard from her husband since he left for a business trip before the incident.
Will uses the chance to take a shower, Ricki does maintenance on the car, and Tom fills up their water bottles. Meg can’t stop herself from having a breakdown, thinking her husband will never come back. A sympathetic Will tries his best to comfort her and promises it’ll be fine, but he can’t stay.
Then the trio returns to the road. Some smoke nearby gets their attention and they discover a crashed military plane. Ricki wonders if it was shot down.
Sometime later they arrive at a water park and decide to look for supplies. Ricki jumps into a pool hoping to go for a swim, but the water is very hot. After watching a military helicopter fly by, they begin their search.
The register is missing all the cash and all the cars had their tires slashed, but at least they can fill the gas cans. Tom struggles to lift them because of his injury and Will has to take over. That night when they drive past an antenna, all their phones begin buzzing.
Tom has a voicemail from Samantha telling him she loves him, but the message is full of static and ends before she can say more. When Tom tries to call Paula, it doesn’t work. Suddenly they see a line of people walking on the road while coughing.
There’s smoke in the distance and when they come closer they discover the whole area is on fire. Ricki thinks they should turn back but Will points out this is their only option. As they cross the area, smoke and ash surround the car.
Will stops driving when he finds a woman in the middle of the road and she explains she has a flat tire. Ricki and Will want to help her, but some armed men come out of hiding. It turns out they forced the woman to act as bait.
These guys try to steal their fuel and Will tries to fight one, but the man easily knocks him down with just a few hits. When Tom tries to reach for his own gun, he pulls his broken ribs and falls in overwhelming pain. After forcing Rick to fill their tank, the men steal all the gas cans and take off.
The trio gets in their car and Will asks the woman to come with them, but she wants to stay with her unconscious husband. A car chase ensues through the smoke and the robbers open fire, so Will responds by hitting their car with his. Tom keeps on coughing and can barely move, so he gives the gun to Ricki.
After a few missed shots, she manages to shoot the men’s tires and causes their car to crash. Once it lands on its roof, Ricki rushes to take the gas cans, however a man refuses to let go of them. There’s lots of struggle until she finally gets one can back and Will urges her to run because he’s seen a fuel leak.
Fortunately they’re far enough when the car explodes. Moments later Ricki asks Will to stop the car. She rushes out and has a breakdown as she realizes she killed the men by making their car crash.
Tom and Will remind her that she saved them, but still let her have a moment to herself. By the time the sun rises, Ricki is still not back. Will calls her name but there’s no answer, he also notices her things are gone.
Tom admits they shouldn’t have asked her to come. As the trip continues, Tom starts coughing up blood. They stop when they find a crash site with cars and a whole train, so Will goes to get any fuel he can find.
When he comes back he finds Tom unable to breathe because his lungs are collapsing. To get the pressure out, Will inserts a needle into Tom’s chest, which helps him breathe again. After they take off, Tom asks Will to promise to take good care of Samantha.
They bond over family histories and Tom finally admits Will is a good man. It turns out he knows Samantha is pregnant and now knows that Will is going to be a good father. In the evening, they cross a bridge and notice lots of abandoned cars.
When they find the way blocked by a bunch of armed men, Will explains that his friend needs medical attention. The creepy group tells him to bring the car forward, but Will can tell it’s a trap and starts driving in reverse. Two guys chase him on bikes while Will turns the car around and shoots at the armed men standing nearby.
Then he does some sudden turns to make both bikers crash. Now the duo can drive ahead again, but there’s still a truck blocking the way. Tom opens fire while Will sways the car, allowing them to make the truck crash to the side and drive through the end of the bridge to finally leave.
Sadly the strain is too much for Tom and he dies in the back seat. Moments later Will stops the car to stare at the body and think about what to do. He decides to keep driving, only for the car to break down in the middle of the road when night falls.
After yelling in frustration, Will covers the car and Tom’s body with fuel and lights them on fire as a final goodbye. The next day Will continues to walk while the occasional driver that passes by ignores him. Eventually a car finally stops and the family agrees to give him a ride, but the man makes Will hand over the gun first.
During the trip they try to use the radio to no avail. Moments later the group makes it to a house belonging to Will’s father and he tells the family they can stay. After sleeping for a few hours to rest, Will tells the family they can have all the supplies here in exchange for their car, and the man agrees.
Before leaving, Will retrieves his gun. The following day Will finds a city in ruins but he still keeps going. Eventually he finally makes it to Seattle, where ash is falling from the sky.
There are lots of abandoned cars and he enters a fire truck to get a gas mask. Then Will continues on foot, noticing all the bodies inside the cars. When he looks at the city, he sees smoke coming out of most buildings.
He crosses the streets while dodging all the crashed vehicles until he reaches his apartment building. By climbing the fire escape he enters his place through a window, only to discover that half the building has collapsed. On a wall, there’s a message from Samantha telling him where to find her.
Afterward Will drives as fast as he can to the address. Jeremiah receives him with a gun but Samantha stops him and runs to reunite with her boyfriend. Once they settle down, Will tells her about her dad, saying he wouldn’t have survived without him.
That night Will is woken up by a rumbling sound. He goes out to investigate and sees the northern lights in the sky. Samantha and Jeremiah are drinking at a campfire so he joins them.
They tell him how the city was hit by a supposed earthquake and the cops made everyone evacuate at the last second. However Jeremiah doesn’t think it was an earthquake, he thinks a nuclear bomb hit the coast and a virus took down the grid before anyone could figure out what happened. Will doesn’t believe it and Jeremiah continues to freak him out when he asks to see his gun.
In private, Samantha assures Will she doesn’t believe the bomb story either and the couple gets naughty. Later Will goes to the bathroom and sees Jeremiah checking out his car. The next morning Jeremiah apologizes for his babbling last night, saying it was the alcohol.
Will confronts him about the car and Jeremiah claims he saw two kids trying to steal stuff. Apparently those kids ran to the woods, so the men go looking for them but only find deer. Then Will tells Jeremiah that he and Samantha are leaving, so he can come along.
Jeremiah says that Samantha wants to stay and turns around with his gun ready to shoot, only for Will to shoot him first. There’s a huge dark cloud approaching at terrifying speed, so Will runs to get Samantha and they escape in the car. The cloud is storming through the area as the couple speeds through the road, hoping they can survive the chase.
