Martin Sloan, driving through the country, stops for an oil change and lube job. He decides to pass the time by walking to the nearby town of Homewood which happens to be his home town.
He is struck by how things seem to be the same as when he was a boy. At a drug store, he sits at the soda fountain and remembers the original proprietor, Old Man Wilson, while he chats with the soda jerk and is surprised when a soda with three scoops of ice cream only costs ten cents.
He thanks the soda jerk for the soda and leaves. The man checks the syrup levels and goes up to the store room and tells Mr. Wilson that they will need more chocolate.
Martin walks through town and remembers who lived in each house when he encounters a little boy playing marbles. He asks the boy if the marbles are still named as he used to do when he was young. He points out his old house across the street and is amazed that the boy identifies it as the Sloan house. Martin introduces himself only to have the boy protest that he is not Marty Sloan as he knows Marty Sloan. The boy runs off before Martin can debate the issue.
At the local park, Martin helps a mother retrieve her playful son from a tree before waxing on about the wonders of summer. He stops when he spots a boy sitting on the bandstand fence. Moving closer, he sees the boy carve "Martin Sloan" into the post - exactly as he had done when he was eleven. Stunned, he realizes the boy looks exactly as he did. Young Martin is frightened by this stranger and runs off.
Martin knocks on the door of his old home and is moved to see his father - dead many years now - answer the door. His mother appears, too, and he tries in vain to convince them that he is their son. Believing he is a lunatic, they shut the door in his face. Not knowing what to do now, he is addressed by a young man next door who is washing his brand new car - a 1934 roadster complete with a rumble seat.
As he walks through the neighborhood that afternoon, thinking, he realizes that he has gone back in time. He returns to his home and encounters his father again. Mr. Sloan does not believe this man is his son despite Martin's uncanny knowledge of the details of the Sloan family. His mother appears again and he tries to convince her of his identity by showing her his driver's license. She pushes them down and slaps him.
Understanding that he really just wants to talk to young Martin, he runs off and finds the boy on the merry-go-round at the park. He runs through it, calling for his young self. But Marty Sloan sees the strange man from before and attempts to flee. He trips and falls, getting his leg caught in the gears of the merry-go-round which causes an injury that brings the adult Martin to his knees as well.
As the boy is carried off, Martin tries to tell him that he only wanted to explain that the best time of his life is now and not to waste it or take it for granted. When he is an adult, he won't have the pleasures of his childhood anymore.
As he bemoans his failure, he sits on the merry-go-round for some time until his father arrives. He tells him the boy will be alright but will have a limp. He also tells Martin that he looked through the wallet that was left at the house. The driver's license and other cards identify this man as being Martin Sloan but are dated 25 years in the future. Sloan understands now that this man is his son but does not understand how or why he is here now.
Martin explains that his life in the city is hectic and he has grown tired. Nostalgic for his childhood, he came back in the hopes of reliving some of those memories again.
Sloan knows that this is a common desire for most people, but Martin knows things that will happen in the future and he will have to leave. Martin knows this but doesn't understand why. Sloan gently tells his son that his childhood is gone. "Maybe there's just one summer to every customer. That little boy, the one I know, this is his summer, just as it was yours once. Don't make him share it!" He urges Martin to look for the positive things in his own present and not to live in the past. They part and Martin boards the merry-go-round which begins turning.
Later, Martin enters the drug store again to find a modern gathering spot for teens. He sits at the same soda fountain and is served by a younger soda jerk who starts to make him an ice cream soda with three scoops (but for 35 cents!) and remembers that Old Man Wilson died about 15 years before. Martin changes his mind about the soda and starts to get off the tall stool when he has a problem with his leg. He explains he injured it on a merry-go-round when he was a kid. The soda jerk remembers the attraction was condemned a few years ago and torn down. But jokes that it was obviously a little late for Martin. Distracted, Martin agrees and goes back to his car.