In 1860 Baltimore, Benjamin is born with the physical appearance of a 70-year-old man, already capable of speech. His father Roger invites neighborhood boys to play with him and orders him to play with children's toys, but Benjamin obeys only to please his father. At five, Benjamin is sent to kindergarten but is quickly withdrawn after he repeatedly falls asleep during child activities.
At the age of 18, Benjamin enrolls in Yale College, but is sent home by officials, who think he is a 50-year-old lunatic. When Benjamin turns 20, the Button family realizes that he is aging backward.