Young baseball fan Yankee Irving, whose father Stanley works as a janitor for New York City's Yankee Stadium, dreams of playing for the Yankees but can't even play sandlot baseball well enough to avoid being picked last. One day beside the sandlot, he finds a talking baseball he names Screwie.
While father and son are in the stadium, a thief steals Babe Ruth's famous bat Darlin', with the result that Yankee's father is blamed and fired. The true thief is Lefty Maginnis, a pitcher for the Chicago Cubs. Lefty works for Cubs owner Napoleon Cross, who desires to see the Cubs defeat the Yankees during the 1932 World Series.