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Character Role Analysis
Lisa
Lisa herself is pretty clueless, and she does little to advance the plot or purpose of the work (except as a means to help Mac network at the camp). She does function in the way a good, solid wall would: she acts as a sounding board for Mac, Jim, and Doc Burton.
Though she formulates no opinions of her own (and does even less), Lisa is able to draw out the contemplative sides of these men—just by sitting there. We learn important things about Jim's past, Mac's desires, and Doc's loneliness just because Lisa exists.