It's an ordinary night in Chicago. Rachel Matheson is hanging out with her kids, five-year-old Charlie and two-year-old Danny, when her husband Ben bursts through the door with an armload of canned food. He orders Rachel to fill the sinks and tubs with water. Her eyes filled with fear, Rachel asks, "It's happening, isn't it?" In Port Royal, South Carolina, Ben's brother Miles speeds down the highway, his buddy Sebastian "Bass" Monroe riding shotgun. They've had a few drinks and are heading back to the Marine base when Miles' phone rings. Ben is hurriedly copying computer files using a strange silver amulet/flash drive as he tries to warn his brother: "It's all going to turn off and it will never ever turn back on!" Their phones go dead, as all the lights in Chicago start to flicker off. Did all of Ben's files download in time? When Miles' car comes to a dead stop, Bass and Miles climb out of the car to watch as all the lights of the cars behind them wink out in a cascade that runs as far as the eye can see, and planes begin hurtling towards earth.
Fifteen years later, all the power in the world is still off, and life in America has changed radically. Car engines, batteries, turbines - nothing works. Governments have fallen. So what caused the blackout? No one knows. Although Rachel has died, Ben, his girlfriend Maggie, Charlie and Danny (now 20 and 17) are living in a small farming town in Wisconsin. Charlie tells her dad she's going hunting, but she challenges Danny to help her explore an abandoned motor home instead, which brings back memories of the way things used to be. Danny opens a cabinet and ancient detritus spills on his head, instantly triggering an asthma attack. Charlie rushes him home, where Maggie, the town doctor, treats him with a foul-tasting tincture. Ben scolds Charlie - she's supposed to watch out for Danny, and she knows the woods and roads aren't safe. When Maggie concurs, Charlie flames out. Maggie's not her mom!
The next morning, Charlie heads to her secret spot to find solace in her old lunchbox, which contains her treasures: a stack of postcards picturing big cities, a defunct iPod, a Rubik's cube. But all is not well in the town. The Militia has come calling, and Ben's instincts are right, they're looking for him. He passes the silver amulet we saw 15 years ago to his buddy Aaron, warning him not to let anyone know he has it. If anything happens to Ben, Aaron is to follow instructions, and keep the amulet safe at all costs. With that, Ben walks up to meet Militia commander Captain Neville, who is indeed looking for Ben, and his brother Miles. Ben is going to come with him, now - or Neville will conscript and re-educate his children. Ben asks for a moment to talk to Maggie, which gives Danny the opportunity to grab a crossbow and aim it at the Militia men.
Ben jumps into the middle of the conflagration, fearing for Danny's life, as other villagers pick up arms in their defense. Minutes away, Charlie's ears perk up when she hears the first gun shot, which hits Ben square in the chest. The villagers open fire, killing several Militia men, but when Neville shoots several of them in quick succession, the insurrection is over. Maggie tries and fails to prevent the soldiers from making off with a devastated Danny, and Charlie makes it back to town just in time to hear her father's final words. Charlie is to travel to Chicago to find Miles. She's going to need his help to get Danny back. Ben reminds Charlie that she's strong, just like her mom. She can do this.
Charlie wastes no time packing up, stuffing her lunchbox of treasures into a knapsack. Maggie insists on coming along, regardless of what Charlie wants. And both women are surprised when they find Aaron waiting for them on the edge of town. He's coming too! Meanwhile, Neville and his men pause at a lake for a break. With Danny chained to the back of a wagon, Neville gently apologizes for the terrible situation. General Monroe will be irate when he finds out what happened to Ben. But when Danny smart mouths Neville, he turns savage in an instant, backhanding Danny across the face, and reminding him that since he drew first, his father's blood is on his hands. After Neville walks away, Danny notices a loose screw on the hook to which he's chained, and starts to work it free.
The next day, Charlie is gathering water from a waterfall when she spies a tall, dark and handsome stranger, fiddling with a bow. While Charlie tells Nate her name, she won't tell him where she's going, nor does she tell Maggie and Aaron about him. Later in the day, the trio find themselves at O'Hare Airport, now abandoned. Maggie doesn't want to stop, but Aaron points out that planes usually have great medical kits, which he knows because he used to own a plane, back when he worked for Google and had $80 million in the bank. Late that night, Danny manages to get the screw loose and free himself. After knocking out his guard with the metal bar, he runs away from the Militia encampment.
Maggie, Aaron and Charlie spend the night in a plane. They're sleeping when three drifters wake them up at knifepoint. As one of them drags Charlie to the front of the plane with ill intent, Maggie offers two others a drink from a bottle in her pack - which ostensibly contains whiskey. In moments, the two guys begin to cough blood and keel over from the poison in the bottle, while Charlie fights off her opponent, who suddenly slumps over dead. Nate has apparently been following them, and is pretty handy with his bow and arrow. By the next day, Nate has joined their band. He tells Maggie that he's headed to Chicago to look for work, but she's still suspicious, and pulls Charlie aside to tell her so. Charlie insists that not all people are monsters - some of them have to be alright.
Dehydrated and hungry, Danny slurps water out of a rain barrel beside a barn. There's a nice home just up the hill, but he falls to his knees in the grips of another asthma attack. Charlie is taken aback by the big city, since Chicago is now a teeming bed of roughnecks. Aaron is surprised to see the change in the once-magnificent Grand Hotel, where he got married before the blackout, and where Ben said Miles might be. The hotel lobby now contains a bar with a homemade still, which is presided over by a surly bartender who denies knowing anything about Miles Matheson. But when Charlie introduces herself and offers the news that Ben is dead, the bartender offers to talk to her - and only her - alone. Nate smirks and pulls a knife, saying, "You're not taking her anywhere." With a casual sleight of hand, the bartender has the knife at Nate's throat in seconds - Charlie is his niece.
Danny wakes up in bed, and staring at the barrel of a rifle held by Grace, the house's occupant. She has recognized his asthma symptoms, and better yet, she has an old inhaler that used to belong to her son. But she wants to know why there are handcuffs dangling off his arm. Danny explains that he escaped the Militia, and doesn't want to cause her any trouble - he'll leave - but clearly, he's too weak to do so. Meanwhile, Danny describes recent events to Miles, who explains that General Monroe thinks Ben knew why the lights went out, and maybe how to turn them back on. If Monroe got the power going, he'd steamroll the continent and butcher the other republics. Charlie's ready to head out immediately to retrieve Danny, but Miles isn't budging. Danny is just bait. Unable to accept this answer, Charlie tearfully begs Miles to help on account of he's family. But he stands by his plans to lay low and out of harm's way.
When Charlie returns to her traveling companions in tears, Nate goes after Miles, who grabs his arm, exposing a Militia tattoo, which all conscripts have. Nate reacts quickly, head-butting Miles, whipping out his bow and backpedaling out the door to the street. Miles realizes Nate has been following Charlie from the get-go in hopes of flushing him out. Now his plan is to drink his prize possession, the last bottle of single malt in Chicago, and wait for the inevitable Militia attack. Miles advises Charlie to leave, and when she won't, he screams at her to "Get out!"
The next day, Captain Neville knocks on Grace's door, to ask if she's seen a dangerous fugitive - Danny. Grace claims Neville is the first person she's seen in weeks, but former insurance adjuster Neville is aces at sensing a lie when he hears it. And then there's the two sets of fresh tracks leading to Grace's back door. Grace capitulates, opening her door. Hearing Neville charging up the stairs, Danny tries to escape out the window, but he's too late, too slow, and back in custody. Meanwhile, Nate returns to the Grand Hotel with a squadron in tow. Miles is waiting for them; he doesn't want to hurt anyone, but he's not "going back." Drawing his weapon of choice, a brass-knuckled sword, Miles leaps into the fray, dispatching Militia men left and right - clearly, he's really, really good at killing...
At one point in the fight, Miles finds himself encircled by Militia, and it looks like his ticket has been punched. That's when Charlie lets an arrow loose, killing a guy, giving Miles a chance to turn the tide. Maggie and Aaron pitch in, as Charlie runs outside, where one of the soldiers attacks her. Things seem fatal until Nate runs up, punches the soldier unconscious, and runs off. Did he just save Charlie's life? After Miles kills the last soldier, he reconvenes with his bottle of single malt, as Maggie sews up his shoulder. Charlie's surprised to learn that Miles has decided to join in her search for Danny - even if they're all going to end up with their heads on a stick.
Miles flashes back to the night the lights went out, when he and his buddy Bass, both sergeants in the Marine Corps, walked back to their base at Parris Island. At the gate, Bass admits he forgot his ID, then pulls up his sleeve to show off his identifying tattoo, an M in a circle - just like the tattoos all Militia men have. That's when it dawns on us: Miles' former best friend Bass is General Monroe, leader of the Militia... A horseman rides up to a massive military encampment. This is Monroe's command center, where his tent is beautifully appointed with luxurious rugs, antiques, even ice! Monroe is not happy when the rider hands him a message from Neville, reporting the death of Ben and capture of Danny.
Finally alone, Grace unlocks her attic door and pulls out a silver amulet, which looks identical to the one Ben gave Aaron on the day of his death. When Grace depresses a tab on the amulet, it powers on, as a single light bulb and a ramshackle computer also come to life. Within seconds, the sound of an old-fashioned dial-up modem can be heard, and then - Grace starts IMing someone with news of Neville's visit!