In a brief note of clarification to his readers, Roald Dahl clarifies that he has not created a traditional autobiography; Boy is not a comprehensive chronology of his childhood. Instead, in Boy, Dahl recounts a number of impactful moments from his childhood, some funny and some sad.

Dahl gives a brief history of his family, including an anecdote from his father’s childhood. Harald Dahl, a young boy living in Norway, falls from the roof of his family home and breaks his arm. A drunk physician misdiagnoses the injury as a dislocation that needs to be pulled into place, and Harald’s broken arm is excruciatingly pulled apart until splinters of bone protrude from his skin. Following this ill-advised treatment, Harald’s arm is amputated at the elbow. He must adjust to life using only one hand, which he manages capably. His only major difficulty, he tells his son, is cutting the top off a boiled egg. Harald and his brother, Oscar, both wanting to make their fortune, decide to move away from their sleepy Norwegian town of Sarpsborg soon after they finish school. After their father forbids them to go, they run away from home, and Oscar ends up owning a fleet of trawlers in the French port town La Rochelle.