Harry Dobbs has built a fully stocked fallout shelter for his family in his basement.  Harry, who is a dedicated gun enthusiast and is sure that his family will be attacked by gangs of bad people at any moment, is big on making sure he will live through any disaster.  He even has a gun range in the shelter, so he can spend the years inside practicing his shooting, if he has to.  Sally, his wife, is hopeless about her situation.  Her husband is far too aggressive for her, and he's scaring their young son by insisting he learn how to shoot; Harry barely knows he has a daughter, because all his interest is centered on the boy. 

Sally leaves to visit her sister in another city, taking the two children with her.  She really appears to be leaving him, though Harry has no idea of what she's planning.  Harry owns a gun shop, and Nick, the friend that works for him, drops by after Sally leaves.  Harry mentions that he would almost welcome a nuclear war, where he and his son could live a basic, simple life with the scum of humanity gone. Harry and Nick are slightly drunk, when Harry decides to tell Nick about the fallout shelter; it had been a big secret till then.  He swears Nick to secrecy.  Harry shows him the radio setup and raises the antennas.  Harry turns on the TV and hears that the Russians are coming.  He calls Sally and tells her to come home; she refuses, and he says to send his son home.  She tells Harry the boy is afraid of him, and hangs up.  Just as this happens, Harry sees a bright light and hears the bomb, as the house ignites.  He and Nick barely have time to jump down into the fallout shelter and seal the door; Harry left the antennas up when he ran upstairs to call Sally, so they're trapped in the shelter with no way of getting any communications from outside.  The radiation level outside is massive, as Harry can see via the sensors by the door.  Nick is worried about his parents, who he lived with, but Harry says they're gone. 

Weeks pass, and they hear noises outside.  Nick thinks they're being rescued, but Harry thinks they're scavengers who would break in and kill them for their food; he's ready to defend the shelter, with all the guns they have.  Three months later Nick is a nervous wreck from worrying, but Nick is in his element.  He's lifting weights to build up his strength, thinking the entire US is gone.  Ten months later he's sure everyone but them are dead.  Nick accuses Harry of being happy about their situation; Harry is mad that he couldn't make a man of Nick, because he's a coward.  Nick says the only thing left for him is to figure out how he wants to die.  Nick leaves the room, and hears the door slam; Nick has left.  A few days later, Nick knocks at the door, but Harry won't let him in because he's contaminated now.  Nick says there is no sunshine above; the town is nothing but garbage.  Nick pleads, but Harry ignores him; he just sits there cleaning the guns. 

After an indeterminate time, Harry is dressing himself in commando garb, and arming himself with an AK47. He's getting ready to leave the shelter and emerge into the cleansed world, or so he thinks.  The camera pans away from the shelter, showing human bones slumped outside the door.  The camera continues to pan over the garbage of the town, and suddenly we see sunlight and life.  A TV newscaster stands before a large dome, saying that it's been a year since a nuclear weapon accidentally detonated in a B1 bomber, destroying the town Harry and Sally lived in.  The site has been covered over to keep the radiation inside, and has become a rallying point for world peace. 

The names of the people who died in the disaster are on plaques in front of the dome, and Harry's name is on it.  Standing there by the plaque are Sally and her two children.  The boy asks if that's where Daddy is buried, and Sally smiles knowingly as she says yes, that's where Daddy is buried.