In the book The Egypt Game, chapter 10, "The Return to Egypt," what is the confusion about the word "sign"?
On Halloween, the three girls make plans to leave the group of trick-or-treaters they will be with to make a brief stop at Egypt. Elizabeth nervously asks what they are going to do, and April says that they will stick close together and wait for a secret omen, or sign, showing them that the time is right to separate from the others. Marshall, who overhears much but usually says little, asks whether the sign will be a pigeon feather, and April replies mysteriously that they will know it when it happens.
As soon as they join the large group, Marshall stops in his tracks and says he wants a sign. The girls are mortified that he would speak publicly about their secrets. He had never blabbed before. They scold him for speaking of their game out loud in the hearing of others, but he clarifies: "Not a secret sign. ... A sign to carry." Melanie realizes that Marshall thinks they are part of a demonstration. He has never gone trick-or-treating before, but he is aware of peace demonstrations that were common in California in the 1960s, the time period in which the book is set.
The confusion about the word "sign" is that the girls think Marshall is referring to the secret omen they discussed earlier, when he really is referring to a physical sign like the sign a demonstrator would carry.