Vernon Simpson is a struggling college chemistry professor. He is also a big baseball fan and each spring his mind wanders off of school and onto the diamond.
He's been developing a formula for a chemical that would keep insects and rodents from penetrating trees. It is nearly finished and would allow him to earn enough money to marry his girlfriend, Debbie, who is also his student and the daughter of the college president.
An errant baseball comes crashing through his laboratory window and ruins his formula. He figures he's ruined. Instead he discovers that the ball that smashed his window got covered with his chemical and is now resistant to wood. When he tries to hit the ball with a tree branch, the ball jumps over the wood, never making contact.
Simpson decides to leave the college and head to St. Louis, to help his team win the pennant. He get a tryout, strikes out everyone, and becomes a pitcher. Not wanting to be discovered by the college he left behind, he names himself King Kelly.
The team assigns a veteran catcher, Monk, to watch over the oddball Kelly. Kelly has great success, though later Debbie discovers who he really is. He eventually wins 38 games for St. Louis, leading them to the World Series. He takes the mound for game seven and....
....you'll have to watch the movie to find out how it ends.
It's a mildly entertaining story, though in today's world it would never fly. He cheats by doctoring up a ball and he's dating a student. No, not today.
The baseball in the movie is not very good. The teams are always referred to by city only, not by name. We assume that the St.Louis team is in the National League because they play Brooklyn. The uniforms are very simple, with no attempt at authenticity.