What metaphors are used in Plain Truth by Jodi Picoult?

She was quiet for a long time, running her finger over the seams of her handiwork. Then she spoke, her voice rising thin as a trail of smoke. "When you're quilting, one missed stitch ruins the whole bunch." With a rustle of covers, she turned to me. "You pull on it," she whispered, "and they all unravel.