Teen baseball fan Johnny Barrows sneaks into the baseball stadium of the Cleveland Indians, then playing in the 1948 World Series; claiming to be an orphan, he befriends team members & broadcaster Mike Jackson. But it develops that Johnny has a troubled home life with his mother and stepfather, and is involved in juvenile crime. His 'better side' shows only when he runs away to visit the team again. Can Mike and the Indians (playing themselves) wrest Johnny away from bad influences?

On the eve of the 1948 World Series playoffs between the Cleveland Indians and the Boston Braves, sportscaster Mike Jackson comes to the Indians' stadium to meet with club president Bill Veeck and the team's manager, Lou Boudreau. Spotting a lone boy playing imaginary ball on the field, the three men applaud his efforts. When the boy, Johnny, tells Mike that he is an orphan, Mike, who is an orphan himself, feels sympathetic and invites him home to spend the night with his wife Katherine and two small daughters. Moved by Johnny's dream of one day becoming a shortstop, Mike invites the boy to the game the next day. After the Indians lose, the team gathers to discuss their strategy when a vendor bursts into their locker room and accuses Johnny of stealing money from his jacket pocket. After Johnny claims that he needed the money to buy a bus ticket back to the orphanage, Mike drives him to juvenile hall to arrange for a ride. As they pull up to the building, Johnny admits that he is not an orphan at all, but lives with his mother in Cleveland. Puzzled by Johnny's lying and stealing, Mike takes Johnny home. On the way, Johnny begins to regret stealing Mike's souvenir baseball, signed by every member of the team, and returns it to Mike. When they arrive at the house, Mike meets Johnny's mother Emily and his hostile stepfather, Carl Novak, who berates the boy for his disappearance. After Mike leaves, Carl slaps Johnny, who then runs upstairs, removes a gun from the footlocker owned by his father, the late Air Force Capt. John Barrows, then goes to meet his juvenile delinquent friend, Dan Hudson. Dan pulls a knife on Johnny and threatens him for deserting him during a heist at the railroad yard the previous evening. Over the following months, Mike befriends Johnny, but as spring approaches, Mike and his family leave for the Indians' training camp in Arizona. Soon after, Johnny arrives in Arizona, claiming that his stepfather has been beating him. Johnny, who is soon appointed assistant bat boy and adopted as a mascot by the team, leads an idyllic life until one day, Carl, who has been alerted to Johnny's whereabouts by Mike, appears to take his stepson home. When Carl and Mike argue about Carl's treatment of the boy, Carl dares Mike to adopt Johnny. When Mike demurs, Johnny, feeling rejected and betrayed, returns to Cleveland with Carl. An embittered Johnny resumes a life of crime. After stealing a car, Dan and Johnny meet at a roadhouse with fences Jake Dawson and Mac. As they negotiate a deal for the car, the police raid the roadhouse and Dawson reveals that he is really police officer Dave Joyce, who has gone undercover to infiltrate a gang of car thieves. In the ensuing fight, Dan pulls his knife on Dave, and because Johnny stops him from stabbing Dave, after Johnny is arrested, the officer recommends that the boy be treated with leniency and remands him to juvenile hall. Upon learning Johnny's fate, Mike and Katherine consider adopting him but harbor reservations about the boy's ability to reform and lead a normal life. When a state-appointed psychologist tells Mike that Johnny's theft of the baseball was a demonstration of his love for him, Mike takes the boy for a ride and questions him about his friendship with Dan. After Johnny explains that he identifies with Dan's anger against his own wayward father and the world, Mike begins to understand the boy's behavior. Under Mike's influence, Johnny's attitude improves, causing the Jacksons' reservations about adopting the boy to evaporate. When the Novaks decide to fight for Johnny's custody, Mike worries that his adoption petition will be denied, prompting the entire Cleveland team to volunteer to act as Johnny's godfathers. At the adoption hearing, Dave testifies that in interviews with the boy's parents, he has determined that Carl believes that Mike has undermined his relationship with Johnny and that Emily has been skittish and uncooperative. During the afternoon recess, Johnny learns that Dan has suffered a nervous breakdown. Dan's condition moves Johnny to reveal to Dave the root of his hatred toward Carl: Right after marrying Carl, Johnny's mother locks away all of his late father's belongings in a footlocker placed in Johnny's room, then reassures her son that to them, his father will never truly be dead. After Dave retells Johnny's story in court, Emily realizes that her actions destroyed any possible relation between Johnny and Carl and begs their forgiveness. After the court awards custody to the Novaks, Mike and Bill convince Johnny to give Carl another chance. When Johnny discovers that Carl has been saving money to send him to the same architectural school that his father attended, Johnny gratefully embraces his stepfather.