In Ethan Frome, how does the story come full circle?

The story comes full circle in its conclusion. When we first meet Zeena we become aware of the fact that it's been her job to care for Ethan's mother. After his mother's death, Zeena becomes ill.... and consequently does nothing. In the end, we come full circle, when Zeena is once again up and about.... caring for her husband, and for Maggie, who is now an invalid.