discuss the refrain "things can change in a day"

When their English cousin, Sophie Mol, and her mother, Margaret Kochamma, arrive on a Christmas visit, Esthappen and Rahel learn that Things Can Change in a Day. That lives can twist into new, ugly shapes, even cease forever, beside their river "graygreen." With fish in it. With the sky and trees in it. And at night, the broken yellow moon in it.