Since virtually the entire content of the short story, "The Scarlet Ibis," is told in retrospect, most of the narrative is of an expository (exposition = background information that contributes to the plot and themes) variety.
The narrator (known simply as the "Big Brother") reflects about his deceased younger sibling, "Doodle." A sickly child from birth, Doodle was not expected to live, much less ever walk or enjoy the normal activities of a boy. But the narrator, spurred in part by his own embarrassment of having a brother with such physical limitations, teaches Doodle to walk. Eventually, the older brother presses Doodle into swimming, climbing trees and other typical boyish frolic, amazing the entire family. But Doodle does have his physical limits, and the narrator's goals for his brother eventually fall short. The turning point of the story comes when a scarlet ibis--not indigenous to the area--appears outside the family home. The ibis tumbles to the ground, dead. Doodle senses that this bird is somehow like him, and the ominous death of the bird foreshadows Doodle's final days.