As the musical opens, Meg Boyd sings with the other wives "Six Months out of Every Year," as Joe Boyd and the other husbands continue their seasonal obsession with America's national pastime, baseball.
After Meg goes to bed, Joe goes out on the porch to ruminate about the appalling fate of his beloved Washington Senators, actually offering his soul in exchange for "one good long ball hitter." Mr. Applegate materializes immediately and offers to make Boyd twenty-two years old and a genuine sports superstar—in exchange for his soul. Boyd agrees, with the stipulation that, should he choose to return to his wife, he has an escape clause he can exercise before the end of the final game of the season. As Meg drifts off to sleep, Joe sings his goodbye to her in "Goodbye Old Girl," while Applegate changes the middle-aged fan into young Joe Hardy, the great baseball player.
Meanwhile, the hapless Washington Senators can't seem to do anything right. Applegate arrives just then with his protégé, Joe Hardy, and gets him to practice and eventually play with the team. Joe immediately becomes the darling of the media, alarming Applegate, who begins to see Joe demonstrating more independence than is wise. He calls up his trusty and beautiful helper, Lola, who assures him she knows just how to captivate Joe.
Joe, however, is lonely and misses his wife. He goes back to his home on the pretext of renting a room. Applegate tries to interfere but only manages to set most of the kitchen on fire, and Joe remains to rent the room and help Meg with chores, something he never attempted before as her husband.
In the meantime, Lola's attempts to seduce Joe fail; and, enraged, Applegate decides to launch a smear campaign against Joe to prevent him from winning.
Act Two begins just days before the end of the season. Washington is leading the league. If they can win the next game, they will clinch the pennant one full day before Applegate's contract matures, and Joe can escape with his soul intact. To prevent the win, Applegate coereces sportswriter Gloria Thorpe into writing a story accusing Joe of accepting a bribe. To defend himelf Joe appears before the baseball commission, and misses this one game—a game the Senators lose without him. The Senators now have one more game—a must win situation—and Joe's contract says his soul goes to Applegate at nine o'clock, whether the game is over or not.
The next morning he tells Applegate and Lola he will play as much of the game as possible, and rack up winning runs before exercising his escape clause and going back to his wife. Furious and bent on revenge, Applegate sends Joe into limbo, hoping to immobilize him during the final game, but Lola follows him, exhorts him to play, and then stalls Applegate.
While Joe plays desperately for Washington, Applegate attempts to foil Joe's final attempt at the bat as the hand of the clock moves toward nine o'clock. At nine exactly, Joe throws down his bat and is instantly transformed into middle-aged Joe Boyd again. Then, taking a final swing at the oncoming ball, he manages to hit one over the wall, winning the pennant for his team.
Back at home, Applegate, with Lola in tow, interrupts Joe's reunion and reconciliation with his beloved wife, Meg, and attempts to seduce him back with promises of the World Series to come. Joe, now locked securely in his wife's arms, escapes the devil's clinches, singing a joyous finale of "A Man Doesn't Know."