i have never read your book, so I don't know what words are the correct anwser, however..
I can provide some general guidance on how to identify words or phrases that suggest a character should be on alert in a story. Look for words that suggest danger or potential harm, such as "warning," "dangerous," "suspicious," "ominous," "threat," or "menacing." Also, pay attention to any shifts in tone or mood in the text, such as a sudden change from a pleasant atmosphere to a more unsettling or sinister one. These can be indicators that something is amiss and that the character should be cautious or vigilant.
If youcan give me the text, i would be happy to tell you the exact words