A neighborhood's power goes out, so they believe that aliens are responsible and that one of them is an alien, so they turn on each other.
If you know and trust someone, don't jump to conclusions about them.
"Maple Street, U.S.A, late summer. A tree-lined little world of front porch gliders, hopscotch, the laughter of children, and the bell of an ice cream vender."
The Monsters are Due on Maple Street
"Sometimes people don't want to hear the truth because they don't want their illusions destroyed." - Freidrich Nietzsche
The neighbors are turning against each other
"Why? Why didn't he come out with the rest of us to look?"
The setting helps reveal the theme because all of the people know and trust each other, but when the power went out, they questioned their close friends.
Charlie didn't trust that whatever was walking towards them wasn't a threat, so he ended up shooting his friend.
"'You'd let whatever's out there walk right over us, wouldn't yuh? Well, some of us won't!' (Charlie swings around, raises the gun, and suddenly pulls the trigger)"
The conflict help reveal the theme because it shows that the neighbors jumped to a conclusion about Les and didn't trust him anymore.
"Les walks toward the group. He stops suddenly as behind him, he car engine starts up all by itself."
The neighbors turned on each other out of fear. The element that helped me figure this out the most was the characters. This is because the characters kept making irrational decisions/theories about their neighbors.