The quote emphasizes the importance of being cautious when answering the door, suggesting that one should always check the peephole first. It serves as a reminder that unexpected dangers, like potential attackers, can appear friendly at first glance. The act of knocking is often associated with harmless visitors, but the statement suggests there’s a deeper threat lurking behind that normality.

In the context of the book "Crossing the Line" by Katie McGarry, this idea reflects a broader theme of vigilance against hidden dangers. It illustrates that people may not always reveal their true intentions, and what seems safe may actually pose significant risks. Overall, this is a call to stay alert and protect oneself from potential harm.