A gang of boys chase Willie through school. When they catch him, they complain that he's too smart and accuse him of being a freak. Willie seems distracted by a little girl walking away and he goes after her. He notes he hasn't seen her before and she introduces herself as Charlotte. Willie knows that it's her mother's name too. They arrive at Charlotte's house and her mother seems to recognize Willie. He mutters knowing and loving her once, and then tries to run away. The bullies are waiting for him and he runs off.
Later at home, Willie writes in his journal that it's time for him to leave and he's trapped in spring. His mother Emma Webley comes in and sees that he's packing, and admits that she's shocked it's time for him to go on. They go downstairs and he tells them that he's going away. Willie shows them photos of all the other families he's been with, going back to 1963. His current father, John, thinks it's a trick but Willie insists that he hasn't changed in over 25 years. As Emma wonders why he's leaving, Willie looks outside and sees Charlotte's mother passing by. He warns that the townsfolk will soon realize he doesn't age, and admits it's been a great three years.
As Willie eats breakfast, he explains that he found them by reading birth notices and when he came to town, he looked for a family that had lost a 12-year-old child recently. He then came to the Webley home and claimed to be lost. But before that 25 years ago, during his first childhood, his parents died and he was sent to the orphanage. As he left, his neighbor, Charlotte's mother, wondered he was going.
At the orphanage, Willie soon realized that he never grew older than 12. The other kids ostracized him when they realized he wasn’t growing. Willie ran away and went to a circus. A dwarf, Tiny Tim, took him in and introduced him to the other freaks. However, they pointed out that he didn't look like one of the little people, and no one would believe he was one of them. Tiny Tim is forced to let him go.
Afterward, Willie walked in the park and noticed an old woman crying. When Willie couldn't pay for an ice cream cone, the old woman bought him ice cream and invited him to sit with her. They bond and then she takes Willie home and explains that her husband died recently and her son died 30 years ago, and now she's alone. She talks about seeing old people become tired, and how it would be nice for children to stay young forever. She invites Willie to stay and he accepts.
Willie decided that he would have to cut himself off from everything else and simply remain young. However, after three years the old woman passed away. As she lies dying, she thanks Willie for their time together and tells him to make someone else happy.
Willie finishes his story and says goodbye to the Webleys. As he walks to the station, one of the bullies comes up to him and starts taunting him. He throws a baseball at Willie, who easily catches it. When the bully wonders how Willie suddenly got so good, Willie throws it back hard enough to make him drop the ball. He tells Willie he'd better get out of town, realizing he's something different. Willie throws the ball at him one more time and then runs to catch his train.
As Willie goes, he sees Charlotte's mother. She realizes who he is and remembers that she was in love with him as a child. However, he has no choice but to move on, crying. Soon, he finds a new family in need of a child.