“The Scarlet Ibis” opens as the unnamed narrator recalls the season in which a scarlet ibis, a brilliant tropical bird, landed in his backyard. This reflection prompts him to remember Doodle, his younger brother, and he begins to narrate the story of Doodle’s birth.

Doodle is born small and unhealthy; his family anticipates he won’t live long and builds a small coffin accordingly. Only Doodle’s superstitious aunt Nicey believes he may survive, citing as evidence the caul (or amniotic membrane) in which he is born. Doodle proves her right, and when he reaches the age of three months without further health complications, the family decides to name him William Armstrong.

Longing for a playmate who can keep him company in his outdoor adventures, the narrator, six years old at the time of his brother’s birth, is disappointed to learn that William Armstrong may never be the companion he envisions: his mother tells him the child may always be feeble and “not all there.” The narrator, deeply dismayed, plans to smother his little brother with a pillow but changes his mind when the infant smiles at him from his bed. The narrator takes this as a sign that his brother’s mind remains unaffected by his physical disabilities.

At the age of two, William Armstrong begins to move about, and at three he learns to crawl. Though the doctors fear the damage physical exertion may inflict on the child’s weak heart, he persists, and with his backward crawling earns the name “Doodle” from his older brother, who thinks he looks like a “doodle-bug.”

As Doodle learns to talk, he develops a deep affection for his older brother, who dutifully but unenthusiastically pulls the smaller boy around in a go-cart. Despite rough treatment, Doodle continues to idolize the narrator and never complains. The narrator, accepting his fate, brings Doodle along on his adventures in Old Woman Swamp.

With regret the narrator recalls the mixture of love and cruelty with which he treated Doodle: he shows his little brother the casket that was once meant for him and makes Doodle touch it. Doodle, always afraid of being left behind, complies despite his terror.

The narrator, seeing Doodle as a source of embarrassment, begins to try to teach his brother to walk against the advice of his mother and Doodle’s doctor. Doodle doggedly persists in what initially appears a fruitless exercise. Little by little he advances, learning first to stand and then to walk. On Doodle’s sixth birthday, the narrator reveals their progress to their delighted family and begins to cry with pride, secretly aware that he has acted in self-interest: Doodle’s inability to walk had brought him shame, so he taught his brother out of pride rather than love.

As the boys walk together on their adventures, they tell each other “lies,” or fantastical stories. The narrator concedes that Doodle’s inventions are better: they are wild, creative tales full of color and wings for flight. They daydream about a future in which they make a living happily picking flowers in Old Woman Swamp.

Encouraged by his success, the narrator begins to teach Doodle to swim, row, climb, and box. He creates an ambitious exercise regimen designed to prepare Doodle for school the following year. Though the brothers experience setbacks as Doodle’s health declines in the winter, spring sees them training once more.

During the summer, a blight followed by a violent storm destroys the crops. World War I rages overseas and the narrator begins to push his little brother harder, testing the limits of his endurance and affecting his health. He fears his brother has fallen behind and will not be ready for the beginning of school. To Doodle the narrator emphasizes the importance of not appearing different from his classmates.

One afternoon, a mysterious injured bird appears in “the bleeding tree” in the backyard. Large and brilliant red, the bird is clearly tropical. It dies before the family’s eyes and Daddy identifies it as a scarlet ibis. Deeply affected, Doodle buries the bird in the garden by himself. After lunch, Doodle and the narrator go rowing, but Doodle is tired and a storm is on the horizon. They hurry home and the narrator, determined to push his brother and frustrated by the weakness he has seen in him, begins to run as thunder rolls. A terrified Doodle cries out for him to wait, but the narrator does not slow. When Doodle doesn’t appear behind him after several minutes, his brother becomes apprehensive. On circling back, the narrator finds Doodle dead, blood running from his mouth. He attempts to protect his fallen brother, whom he compares to the scarlet ibis, from the rain.