"I was in school when the ships came," a little kid's voice tells us. We didn't use nuclear bombs because we thought they might be friendly, but they weren't. They used something that stopped all the machines. They wiped out the army. Moms and dads fought.
The aliens kill grown-ups and catch kids and put devices on them to control them.
Matt, the young boy, thinks the aliens might have gotten his brother Ben. His dad is out fighting.
Tom Mason (Noah Wylie) runs in bombed out streets, going after a cart of food. Laser shots take out the cart and they're forced to leave it. He and his son Hal run between burning cars, trying to avoid the hail of gunfire. There are live aliens, called "skitters", and mechanical ones called "mechs".
Other resistance fighters put down cover fire.
Tom and Hal hide under a car, they're helpless to aid a woman who gets shot and is wounded, then preyed upon by aliens.
Tom meets up with more fighters, who tell him the aliens are on the verge of taking a key part of the city. They watch as a cloud of something envelopes the city behind them.
Back at camp, they report their casualties and walk through throngs of hungry people warming themselves by burning oil drums. Tom checks on his son, Matt.
Anne (Moon Bloodgood) tells Tom about her talk with Matt and the pictures he drew. She's encouraged that he's drawing his whole family.
Tom is summoned by the commander, Porter, who tells him it's time to leave the city because they've picked it clean. Tom doesn't want to leave the kids that the aliens have taken hostage. The commander says they'll travel in packs of 300, with 100 fighters and 200 civilians each. He's already sent out 9 units. He tells Sam he'll have Jeffries as his second in command.
Weaver (Will Patton) will have the Second Massachusetts, replacing Jameson. He's giving him Tom as his second in command. Weaver wants to stay and fight, but Porter points out they don't know how to fight them, so they have to run and hide instead.
He tells them they're trying to figure out the "harness situation" -- the vertebrae braces the aliens put on children.
When Weaver leaves, Porter tells Tom to use his degree in military history to defend the civilians.
Around the campfire later, they tell stories of impressive alien kills. Hal looks at the alien ship parked on the horizon and muses about infiltrating it and blowing it up.
Tom suggests a few historical approaches, including tunneling under it with TNT, and earns the name "Professor Kicka---."
Hal asks his dad to ease up on the history lessons when his friends are around. Even post-alien invasion, he's embarrassed by dad.
Anne treats the wounded. She's a pediatrician. She asks Tom what the plan is. "Retreat, regroup, return, revenge," he tells her.
Weaver barks orders at Tom like they're in the military.
Matt wonders if he'll still get a birthday party when they're on the move.
Everyone packs up to head out. Tom looks over stacks of books. He weighs Tale of Two Cities and 20,000 Leagues Under the Sea and takes the lighter one -- Dickens.
They head out.
They walk through a neighborhood and Anne remembers visiting one of the houses once with her husband. He was a painter.
They stop to pick over the food supplies. Weaver laments that they're moving slowly with all the civilians. Tom suggests he take a small group of fighters and go back for food since Weaver won't detour with the whole group.
Weaver agrees. Tom rounds up six people, including Dai, who comes with a stick of C4.
Matt tells his dad about his birthday wish. He wants everything back the way it was.
Tom looks at maps, with Hal and Karen set to scout the food locations out.
Waiting for Hal to return, Tom finds a boy's body lying nearby. He had a harness on. Someone tried to take it off him and it killed him. He's about the same age as Tom's son Ben.
Hal surveys the food location and hears aliens coming. He ducks for cover by a stream. He sees a dozen children walk by like zombies. They have harnesses on. One is his brother.
Back with his dad, Hal wants to get his brother, despite the odds. Tom has to tell him they can't. Hal tries to leave, but Tom wrestles him to the ground and tells him they have get the food first and plan better.
Tom draws up a plan. He'll go in at dark with Dai and Hal and if the coast is clear the rest should follow. If they hear shots, he tells them, they should leave.
He tells them they don't have to kill them all, just enough to make trouble. "We can make it too painful and too costly for them to stay," he says.
Tom tells them history is full of invading forces leaving because inferior forces made too much trouble. When his historical examples don't work, he cites Red Sox-Yankees in 2004. "We can beat 'em," he says.
After night has fallen, the three sneak into the warehouse. They creep along the aisles. It seems empty. They signal for the Jeep. They start loading it up quietly. As they're packing, an alien hand appears. It leaps out at Hal as he's unloading food. Tom comes and shoots at it, but he's soon taking fire. He runs for cover and arms the C-4. One of the mechs stalks them.
Tom wheels a cart toward it with the C4 and blasts it to bits. Now he has to contend with the skitter. It has him down on the ground and cornered, but Dai saves him by shooting it. It dies slowly, making burbling noises.
Tom and the group meet the others at the designated bridge, bringing a Jeep full of food.
Tom brings some in to Weaver, who asks "What took you so long?"
Tom tells Weaver about Ben. After they accomplish their next mission of taking the armory, Tom wants to go back to get Ben. Weaver says as his commanding officer, they're not allowed. But Tom asks what he would do if he had a chance to get his kids back.
Tom says it's possible to kill them, you just have to get close.
Matt enjoys a birthday cupcake from Anne. Hal brings him a present, saying it's from Tom. It's a fancy skateboard like he used to have, a Ripstik. He straps on a helmet and wheels around as everyone watches. He lets the other kids try it out until Weaver signals it's time to go.
At night, Tom and Dai scope out the armory. There are fresh alien tracks.
Hal throws a ball for a dog to chase. But the dog doesn't retreat when a mech comes at it. Jimmy, who is 13, runs after the dog and Tom narrowly saves him from alien fire.
Matt wakes up in a real bed in a kid's room. Tom comes to get him. They're moving out from the houses they've been staying in. Tom's planning to go look for Ben later.
He checks in with Weaver, who thinks they failed in their mission because they had to retreat. Weaver says that means Tom can't go look for Ben like they agreed.
Anne asks Weaver why the fighters are getting to sleep in houses while the civilians are in tents. He makes the case that it's because his fighters need rest and the civilians would be too hard to mobilize out of houses.
Weaver tells her the civilians are welcome to leave if they don't like his rules. She tells him they're not just "eaters" like some soldiers call them. They cook, clean and haul trash. Weaver says the civilians concerns don't matter until the fight is over.
Tom gets oatmeal and walks around the civilian camp with Anne. He thinks civilians are "a liability and a hindrance." But they're the best reason they have to fight.
Uncle Scott leads school for the kids, telling them about biology. Later, he talks with Tom about the fact the skitters have six legs and the mecs have two and wonders what this means about the aliens.
Hal talks to a dad who's looking for his son who was also taken. He wants to tag along when they look for the kids.
Lourdes follows Hal around, irritating Karen.
Karen and Hal go into one of the houses and wonder about the girl who's room they're in. Karen teases Hal about Lourdes, but he assures Karen she's the only one. They're about to kiss when Tom comes in to tell them they're going back to the armory tonight on Weaver's orders.
Karen thinks it's a waste of time.
Tom rounds up the fighters to go out, but tells Jimmy to stay. They tell him it's because they need someone bigger in case they find weapons.
Weaver tells him reassuringly that he's a good soldier.
Back at the armory, Tom and his people go in. One of them gets hit by two arrows. They exchange fire with a person, who tells them to put down their guns and turn over their weapons. He shows Tom they have Karen and Hal.
Tom puts his guns down just in time for a mech to drop through the ceiling.
One of the scavengers is hit in the leg, so his people carry him and march Tom and his people with hoods on like prisoners.
They remove their hoods so they can see they're in a school auditorium. Tom says they're just a group of people trying to survive, not part of a resistance.
The leader, Pope, wants to talk the girl (Karen) and the boy (Hal), but no one else. He holds a sword on Tom, then pulls a gun. Hal speaks up to save his dad, saying they can get them more guns and are part of the Second Massachusetts resistance.
The marauders know all about them. They've been watching them for two days. Pope's brother was wounded and lies unconscious on the stage.
Pope guesses that Tom is Hal's dad. He says they're not going to kill anybody because they're way too valuable. He wants to make a deal for the .50 caliber gun back at camp. He calls for a girl named Maggie in his group to take Hal and the terms of their deal back to camp.
With everyone else taken away, Pope tells Tom the invasion is the best thing that ever happened to him. Tom eyes the gun strapped to Pope's brother's leg on the stage nearby. Pope says they've been having a blast.
Maggie marches a hooded Hal back toward camp. He makes a move on her, but she knocks him down and pulls a knife on him. She warns him if he pulls anything again, she'll shoot.
Pope continues talking at Tom, who seems to be trying to get free of his bindings. Pope tells Tom the way to kill the aliens, whom he calls "Cooties", is by taking out a few legs to slow them down, then going for the head.
He tells Tom the ships are drawn to heat, so they lit an engine block on fire to draw one. They fired at it with their bazooka, but the ship dodged it.
Tom asks for a beer and Pope goes to get it.
Maggie releases Hal outside their camp and tells him he has an hour to return.
In a house, Anne tries again to talk to Weaver about housing. Hal arrives.
Pope releases Tom and gives him a beer -- it's cold. They've been running a fridge on a generator.
Tom tells Pope about his son being harnessed. Pope says Maggie saw a group of harnessed kids down by the hospital. Tom makes his way over to Pope's brother, but Pope busts him by asking him. He pulls out a gun. He knows Tom's been eyeing the gun the whole time. Tom backs down.
Tom suggests Pope join the resistance, but Pope essentially thinks the resistance is futile.
Weaver calls for Mike and tells him what's going on. Mike asks how they make the trade, but Weaver says they can't or the marauders will just bleed them dry with demands. He orders Anne to get the civilians ready to move. He points out to Hal that they can't go fight them because they don't know where they are.
Weaver orders Mike to watch Hal. Once they're in another room, Mike gives Hal his gun and lets him go. Hal leaves the gun, knowing Maggie might be watching.
He runs into Anne, who says she can help.
She goes with Hal to meet Maggie and tells her she's a doctor.
Maggie comes back. Pope doesn't feel like dealing and tells Anne to fix his brother Billy or he'll kill her.
She stitches up his leg.
Pope takes his guys to go rob the Second Massachusetts. He leaves Maggie and two other people behind to watch Hal and Tom.
Pope summons Weaver with a flare gun. He wants the .50 caliber gun, the GTO and all their food. He says the aliens will see the flare soon and they'll all be dead.
Weaver orders them to leave the food and promises Pope he'll find him.
Back in the auditorium, Billy leers at Karen and demands she stand up and turn around for him. He promises Karen they're going to have a good time. His intentions are not honorable.
Maggie grits her teeth and asks Anne if Billy is going to live. When Anne says yes, Maggie shoots Billy and then Cue Ball, Pope's only men there. She tells them they each deserved to die.
Back at the field, Weaver is leading people away when he hears gunfire. Tom's people are firing on Pope. Anne tells Weaver to get everyone to follow them.
One of Pope's guys tries to shoot the .50 caliber, but Tom and his guys shred him. Tom reminds Pope the ships are going to target the flares and he's sitting in the middle of them. Tom tells him to join or die.
Instead, Pope hops in the GTO with the .50 caliber mounted on top and drives away, leaving his men to get incinerated by the alien ships. He doesn't get far before Weaver stops him and disarms him.
They make camp at a school.
Tom checks in with Weaver, who is not happy with how things went down. He reminds Tom about the chain of the command and reminds him to follow it when he gets back. Weaver is sticking to his word that they can go for Ben. He gives them three days.
Tom takes Pope to his cell. Maggie has chosen to stay and earn her citizenship as a fighter.
"I'll take a rest for a while," Pope says. "Being the leader of a post-apocalyptic gang of outlaws has been exhausting."
Tom and Hal prepare to go look for Ben with Dai and Karen. Maggie shows them the way.