What kept Marshall busy when he had nothing else to do? What might the author be foreshadowing?
The answer to this question can be found in chapter five which is titled "The Evil God and the Secret Spy." The chapter begins with April, Melanie, and Marshall heading back to the abandoned lot. Everything is exactly how it was before, so the girls are even more convinced that nobody ever goes there. They begin to clean the place up, and as they are clearing out trash and other debris, they notice the locked gate and the Professor's window. There is some initial worry about the Professor watching them, but they realize that the window is so dirty that he couldn't see through it anyway. The girls return to having a sense of security and sit down to make plans. As they are making plans, Marshall is occupying his own time. He is digging a hole in the middle of the yard with a sharp stick. Security is tightly wrapped around him, so he has both hands free to dig.
As for what the author might be foreshadowing by this very small piece of information, that is up to an individual reader's thoughts. If the reader is knowledgeable about the Chekhov's Gun concept, then the reader is likely to be suspicious that either the stick or the hole is going to be of future importance. If the reader feels that the hole is meaningless but the description of Security is important, then the reader might think that something is being foreshadowed about Marshall losing Security.
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