The Narrator's younger brother, William Armstrong (later nicknamed Doodle), was born an invalid. His parents didn't think he would live and made preparations for his death. The older brother, at first, is skeptical about Doodle, and even has thoughts of killing him out of embarrassment, but later he decides to teach Doodle to be like other children because of his own pride. They go to the "Old Woman Swamp" to practice their plot. The older brother gives him a deadline to be like other children and attend school. He taught him to run, ride a bike, and tried to teach him to jump far. His grueling work shows little progress as the deadline he sets gets closer. Shortly after, the two children find a dead scarlet ibis that was blown over by a storm from the tropics. Doodle's father notes that the bird must have flown quite a vast distance to end up dying here. "A scarlet ibis! How many miles it had traveled to die like this, in our yard, beneath the bleeding tree."
Doodle and the older brother set out to the bog for one final attempt to yield results, and Doodle fails. As a storm approaches they start to make their way back to their house. Frustrated that his plans had come to naught, the older brother begins to run faster than Doodle, leaving him behind in the storm. After his rage dies out, he starts feeling guilty. Walking back, he finds Doodle curled up next to a nightshade bush, bleeding and presumably dead, with similarities to the dead scarlet ibis they found. The ending line in the story is, "For a long, long time I lay there crying, sheltering my fallen scarlet ibis from the heresy of rain". Although it is generally understood that Doodle is dead, the real explanation of how he died has been left for us to interpret on our own.