Vernon Simpson is a young university chemistry professor working on his doctorate degree and is in love with the university president's daughter, Deborah Greenleaf. Vernon's department head, Prof. Forsythe, tells Greenleaf that upon completion of Simpson's degree, he intends to nominate him as director of a new research laboratory. Unknown to Forsythe, however, Vernon has a major flaw: every spring he becomes absentminded due to his intense interest in baseball. Debbie's father has made it clear to Vernon that, given his current financial situation, he should not be considering marriage to Debbie. However, Vernon tells Debbie that the situation may change very soon as a result of the experiment he is working on. Vernon has been developing a chemical compound to keep insects and other living matter away from wood, and has a major company interested in marketing it. His experimental setup is destroyed, however, after a baseball crashes through his lab window and lands in his chemical "soup" in the sink. When Vernon discovers that chemically coated ball is repelled by wooden objects, he realizes the enormous impact his find could have on the game of baseball. To verify his findings, Vernon arranges to have two student baseball players, Schmidt and Isbell, help him in exchange for additional tutoring. When Vernon throws a baseball that has been rubbed with a cloth soaked in the compound, it repeatedly jumps away from the swung bat and into the catcher's mitt. Although he cannot reconstitute the compound, Vernon immediately asks Prof. Greenleaf for an emergency leave of absence to demonstrate his findings, the details of which he does not reveal to Greenleaf. Vernon takes a train to St. Louis, heads for the baseball stadium and sees manager Jimmy Dolan. Although Vernon bills himself as the pitcher Dolan is in great need of, Dolan tries to have him thrown out. Club owner Stone, however, arranges for him to demonstrate his prowess, fully expecting him to be humiliated. Working with Monk Lanigan as his catcher, Vernon strikes out the team's top batters, and Stone realizes they have found a new star. After Vernon, who is playing under the name King Kelly, wins the first game he plays in against Chicago, he negotiates a lucrative contract with Dolan and Stone. Dolan assigns Monk to room with Vernon and keep an eye on him, as Dolan thinks Vernon is a "screwball." When Monk notices the bottle containing the chemical compound among Vernon's belongings, Vernon tells him that it is a prescription hair tonic. Vernon then reads a newspaper item reporting that he is missing and that a search has been initiated. After Vernon sends Debbie a diamond ring along with a vague letter asking her to have the police call off the search, Debbie's father thinks Vernon is probably mixed up with racketeers. Later, Debbie's mother spots Vernon at a railroad station in the company of a bunch of tough looking players and assumes they are gangsters. Vernon wins games in Pittsburgh, Philadelphia, Brooklyn and New York but has to insist that the press take no photographs of him. Meanwhile, Debbie reads a newspaper account about a gang robbing an exclusive jewelry store and removes her ring. When Vernon makes a payment on the ring, he bumps into Debbie, who accuses him of being a gangster. He confesses that he is now a baseball player but Debbie refuses to believe him. Vernon and his compound win every game for the team. One afternoon, Debbie attends a game and, through binoculars, recognizes Vernon. During the game, Monk, Vernon's regular catcher, injures a finger and has to have wooden splints applied to it, causing the ball not only to avoid the bat but Monk's hand as well. The team eventually wins the pennant and is scheduled to play against New York in the World Series, starting in St. Louis. Debbie tells her mother that Vernon is the new baseball sensation, and her father soon finds out the truth as well. Just before Vernon is to pitch the opening game, Dolan to whom Monk has loaned Vernon's bottle of "hair tonic," he returns it to Vernon and accidentally drops it. The bottle breaks, leaving Vernon with no compound to rub on the ball. With Debbie and her parents watching in the stands, Vernon struggles through the game and manages to win by catching a hit with his pitching hand. X-rays reveal that the hand is broken and that he will not be able to play any more. Monk sees Vernon off at the station then phones Debbie. A big crowd, led by Debbie, welcomes Vernon home. Dr. Greenleaf tells him that Stone has given the university money for a new research laboratory and that he will be appointed director.