Susan Coolidge's What Katy Did is the story of 22-year-old Katy, who continuously makes and rapidly breaks her commitments about how she will change her actions and treat others, especially her five younger siblings, with more respect and comfort.

When Katy meets her cousin Helen, an invalid, Katy is awed by her sweetness and generosity.

Meanwhile, Katy decides to be like her cousin. Although Katy has an opportunity to be more like her cousin Helen, she wishes she hadn't been restricted to her bedroom for four years because of her accident.

The author's main focus in this story is the change Katy goes through during her sickness.

When Katy learned her lessons about how to really take care of others, she realized she had recovered the capacity to walk.

The journey of a girl and the changes she goes through are described wonderfully.