Jack Keefe, a baseball pitcher, is called up from the minor leagues to the Chicago White Sox, where he begins corresponding with his friend Al Blanchard through letters. Despite their friendship, Jack is incapable of genuine emotional connection and comes off as patronizing and egotistical. His correspondence serves as an outlet for his braggadocio, and Al remains oblivious to Jack's true nature.

Jack's Self-Absorbed Narratives

Overflowing with unwarranted self-confidence, Jack believes every trivial event of his life is noteworthy, recording them with vivid detail in his letters. Utterly lacking in modesty, he even recounts incidents that expose his foolishness. Upon arriving at the West Coast training camp, he quickly irritates the team’s manager with his overeating, disdain for instructions, and overall laziness. Although a powerful right-handed pitcher, Jack neglects his fielding duties and pays little attention to base runners. The manager's attempts to correct him with irony are lost on Jack. On days when his pitching falters, he attributes his struggles to a sore arm or blames the fielders, umpires, and scorers for his misfortunes. Jack also believes himself irresistible to women; during training camp, he meets Violet from Detroit, intending to pursue her when the team visits her city.

A Rocky Start in the Major Leagues

Jack performs adequately in spring training, securing a place on the White Sox roster. However, in his first start against the Tigers, he delivers a dismal performance, allowing sixteen runs to score and witnessing Ty Cobb steal four bases. The manager, fed up with Jack's attitude, punishes him by leaving him in the game, yet Jack blames his failure on a sore arm. Subsequently, the manager trades him to a San Francisco minor-league team, and Violet derisively calls him a "busher." Despite threatening to quit baseball, Jack reluctantly reports to the new team.

Love and Loss in San Francisco

In San Francisco, Jack turns his luck around by winning eleven consecutive games and becomes engaged to a woman named Hazel. After being recalled to the White Sox, he pitches well in a series against the Cubs. Hazel requests a hundred dollars from him to cover her travel to Chicago for their wedding, but Jack sends only thirty, prompting Hazel to marry a boxer instead. Undeterred, Jack seeks to marry Violet, only to find she has wed another ballplayer. Ultimately, Jack settles down with Florrie, the sister-in-law of Allen, a left-handed White Sox player.

Domestic Strife and Financial Troubles

Florrie refuses to spend winter in Jack’s hometown of Bedford, leading them to rent an apartment near Allen and his wife Marie. Frequent spats erupt between the couples, fueled by Jack's notorious stinginess. Holding the belief that all left-handers are inherently mad, Jack's conflict with Allen reinforces this conviction. When Allen plans to bring Marie to spring training, Florrie wishes to accompany Jack, but he claims it's unaffordable. Feeling underpaid, Jack attempts to negotiate a raise from the team despite a signed contract, but Charles Comiskey, the Sox's owner, refuses his request.

Jack's Professional Predicament

In a bid to join the Federal League, which is scouring players from rival leagues, Jack’s plans are thwarted when they refuse to contract him due to his commitment to the White Sox. Upon learning of his attempted defection, the White Sox demote him to a Milwaukee minor-league team. Florrie leaves him, and Jack, resistant to another minor-league stint, borrows money from Al and returns to Bedford. Eventually, the White Sox retain Jack due to a waiver rule technicality. Though he arrives at spring training overweight after indulgent winter habits, the manager's dietary restrictions whip him back into shape, earning...