A sunny early evening on the 300 block of Maple Street. At 6:43 pm, there's a bright flash of light and a roar. Everyone stares up at the sky, and the adults figure that it's a meteor. However, none of them heard a crash. Steve Brand's wife come out briefly and her husband told her what happened, and she goes back inside.
Soon, people throughout the neighborhood discover that the power and the telephone lines are out. Steve's wife tells him about it and the other neighbors come out. One man, Pete Van Horn, offers to cut across the yard and see if the power is out on the next street. Steve meets with his neighbors Charlie and Don, and Charlie suggests that they check with the police. One woman points out that the radio isn't broadcasting, and Steve gets in his car to drive downtown. However, his car refuses to turn over even though it was working fine a few minutes ago and the tank is full.
Charlie and Steve start walking but one boy, Tommy, warns that "they " don't want them to leave. He figures that aliens were in the thing that passed overhead, and insists that the power goes out in every science fiction book that he's ever read. Steve insists that it was a meteor that caused the power failure. Tommy begs him not to leave, warning that he won't be able to get into town. The only people who could leave where the aliens' advance spies, posing as humans. Steve asks for more information, and Tommy says that the aliens sent a family of four ahead to prepare for their invasion. Joking, Steve suggests that they run a check to see which of them are human.
Another neighbor, Les Goodman, tries to start his car without success. As he joins the others, his car starts up on its own. His neighbors wonder how it started, and Don points out that Les wasn't interested in seeing the flying object. Charlie says that the Goodmans have always been oddballs, and everyone goes over to the Goodman house. However, Steve stops them and says that they can't be a mob. The car stops, and Les tells the others that he has no idea what's going on. Don demands an explanation and Charlie and the others join in. Les admits that it's a freak thing but it doesn't make him a criminal, and Steve says that they're on a monster kick now.
As Les complains, his car starts again with no one near it. He reminds them that they've been there for five years, and the whole thing is just weird. One woman speaks up and tells him to explain, and Don tells her to continue. She says that a couple of times late at night, she's seen Les standing in his yard looking up at the sky. Les says that he has insomnia and steps forward, and everyone back away. Angry, he tells them that they're sick people and warns that they don't know what they're starting.
Later, Les's wife set out candles and goes out to her husband. Les is standing watch on the porch, and the neighbors are watching his house from their yards. Charlie's wife points out to her husband that they've known the Goodmans for years and they've been good friends. Charlie figures that there's something wrong with Les, and they're not dealing with normal circumstances.
Steve approaches the Goodman house and Les warns that anyone setting foot on his porch is asking for trouble. His wife insists that it's madness and Steve agrees. Charlie yells to Steve, warning that he isn't above suspicion. He says that somebody will tip their hand eventually, and Steve tells him to go inside and shut his mouth. Charlie accuses him of being one of the aliens, and Don says that Steve's wife has been telling people about how he builds a radio in his basement. When Don points out that none of them have seen it, Charlie demands to know who talks to him. Steve blows up at him until his wife Myra intervenes, saying that it's a ham radio she bought for him. When she offers to show it to the neighbors, Steve refuses, telling them to get a search warrant.
As Charlie accuses them of looking for a scapegoat, they hear footsteps approaching. Everyone looks into the darkness and sees a shadowy figure approaching, and Tommy insists that it's the monster. Don grabs a shotgun and Steve grabs it away from him, but Charlie figures that he's going to talk them into the grave. He grabs the shotgun and shoots the figure down. The neighbors go over and discovers that it's Pete Van Horn, who left earlier. Charlie insists that he didn't know who he was, and that he was just defending his friends and family.
The lights in Charlie's house comes on, and the others demand an explanation. Les figures he killed Pete to stop him from telling them something. Horrified, Charlie backs away and Steve grabs him, and Charlie breaks away and runs into his house. The neighbors grab rocks and throw them, hitting Charlie in the head. He shouts that he knows who the alien really is... and points out Tommy. Tommy's mother insists it's not true, but the others point out he's the one who knew what was going to happen. Steve tries to calm them down, and Tommy runs off. His neighbors chase after him, and the lights in another house come on. Then the lights come on in Don's house, and another, and another. Neighbors grab bricks and guns, and attack each other in a fit of panic.
On a hill overlooking Maple Street, two aliens watch in satisfaction. One of them tells the other that all they need to do is stop a few machines, and the humans will pick on their most dangerous enemy: themselves. Now they'll travel from street to street, letting the humans destroy themselves.