In "Ender's Shadow" by Orson Scott Card, the quote "Only a fool closes the door when the wolf is already inside the barn" serves as a metaphor for recognizing dangers too late. It emphasizes the importance of being proactive and vigilant in addressing threats before they escalate. This wisdom underscores the necessity of foresight and awareness in confronting challenges, particularly in areas of personal and communal safety.

The phrase suggests that once a problem is present, it's crucial to act swiftly rather than ignore it until it's too late. It illustrates a common scenario where complacency or denial can lead to dire consequences. Card's message reflects the human need to confront issues head-on rather than trying to contain them after they have already manifested.