Symbolism, Imagery, Allegory
Dreams have to symbolize something, right?
While Neil is in the bootlegger's house, doing whatever it is people do in the bootleggers' houses, Grace falls asleep and has a dream about seeing her uncle, "stooped and baffled, looking out at her, as if she had been away for years and years. As if she had promised to go home and then she had forgotten about it, and in all this time he should have died but he didn't" (252).
You could get very creative with what this dream might symbolize, but some basic possibilities might be regret or the passage of time. Or maybe it represents Grace's supposition that there's a thin line "between some threadbare ways of living that were respectable, and some that were not" (250). Chair caning? Good. Bootlegging? Bad. We know this because society says so. But why does society say so? Why do we listen?