Symbolism, Imagery, Allegory
When Isabel and Ruth leave Mary Finch's home, Robert instructs them to bring nothing along except their shoes and blankets. This means Ruth must leave behind the only possession that's truly hers: a doll "made of flannel bits and calico" (3.1). That's a long way from a Barbie or an American Girl doll, but for a slave, a doll of any kind would be a luxury.
When they arrive at the Locktons', Isabel makes a new doll out of cornhusks and scraps of fabric to replace the old one. In this respect, the doll is a symbol of Isabel's kindness and faithfulness to her sister. She makes Ruth something not only be played with so she can be a child even in the midst of slavery, but also to comfort her and remind her of their old life.
When Madam Lockton sends Ruth away to her estate in Charleston, though, the doll takes on new meaning. In Ruth's absence, it becomes Isabel's comfort object to remind her of her sister, as well as provide the hope that she will someday see Ruth again. To Isabel, not keeping Ruth's doll is like giving up that hope, so when she makes her ill-fated decision to leave to join the British, she hides it inside a rag in a corner of her basket, saying that it's "the one thing I could not leave behind" (28.36). Insofar as it represents her sister, the doll is Isabel's purpose.
As important a reminder as the doll is, though, it eventually becomes a symbol of the sacrifice Isabel is willing to make for others. When fire strikes the city of New York, Isabel willingly drops the doll so she can more easily rescue the helpless Lady Seymour from her burning home. Isabel's a deeply sentimental person, but she's still willing to sacrifice memories of the past for herself and others to stay alive. Nonetheless, it's a painful sacrifice for her to make. "All I lost in the confusion was Ruth's doll," she says. "All I lost was everything" (32.6). Pardon us while we grab a tissue.