The narrator of The Scarlet Ibis and his brother Doodle are close both because of and in spite of Doodle's condition. When Doodle is born, the narrator is disappointed because he "wanted more than anything else someone to race to Horsehead Landing, someone to box with, and someone to perch with in the top fork of the great pine behind the barn." But he is told that his brother will never learn to walk, and the doctors don't give much hope for many other independent living skills, either.
The narrator makes it his mission to help his brother do the things doctors and their parents say is impossible. Far from noble, he honestly assesses that his motivation in doing these things is because of his own pride. When he first secretly teaches his brother to walk when Doodle is six, he cries because he realizes that "Doodle walked only because I was ashamed of having a crippled brother."
He continues to help his brother, but his motivation remains the same. They do share a tenderness, planning for a future that is part realistic and part Doodle's fantasy. The narrator dreams big dreams with his younger brother and enjoys their time together at Old Woman Swamp when the weather is nice and Doodle feels well.
However, the tone becomes more tense when everyone decides that Doodle has progressed so much that he should attend school. The narrator assesses his brother's skills and determines a new schedule of all the skills that Doodle needs before heading to school. Doodle, according to his brother, needs to learn how to swim, row, climb rope vines, and box. Since his younger brother has been told that any exertion could trigger a fatal heart condition, the foreshadowing runs deep that his brother is pushing him too hard.
His brother's health declines; Doodle grows feverish and doesn't sleep well. He suffers with nightmares and overall is just more ill than before. His brother, saddled with his prideful timeline, presses forward relentlessly.
In the final scene, the narrator takes Doodle rowing and has to row back quickly because of an ominous storm brewing. When they return to land, Doodle is frightened and tired and smiles ashamedly at his big brother. Doodle follows his brother closely as they head home, and the narrator says that within him a "streak of cruelty awakened." He runs as fast as he can, leaving his brother behind as Doodle calls out, "Brother, Brother, don't leave me! Don't leave me!"
The narrator doesn't realize it, but this is the last time he will see his brother alive. Doodle dies of the exertion that the doctors warned against in his early years, and his brother is left with the certainty that his own pride is the cause of his brother's death.