The plaque on the family's gates of their home carries a significant quote. The "YOU HAVE BEEN WARNED" is a statement that appears repeatedly in the story. It is meant to serve a threat to would- be criminals that the family is "warning" them of their secured presence. Yet, it might be more for the family themselves, as if they are trying to secure themselves of having nothing to fear when it is fear that exists at the family's core of being.
Another quote that is significant from the story is the state of fear that has gripped the suburban neighborhood. The result of being afraid of crime is that individuals end up living in a walled world, cut off from all beauty and experience in the desire to be "safe:"
When the man and wife and little boy took the pet dog for its walk round the neighborhood streets they no longer paused to admire this show of roses or that perfect lawn; these were hidden behind an array of different varieties of security fences, walls and devices.
I think that this quote is significant because it summarizes the state of the world that the neighborhood has created for themselves. The fear of "the other" is one that has essentially negated any hope for human appreciation of beauty and of living, in general. Walls, devices, and measures of security have created fortresses, instead of homes. The cultured landscape of roses and lawns, elements of beauty to which the neighbors used to aspire, have now been replaced by barricades and measures used to cut off this beauty from the world.