In 1929 LaGuardia runs for mayor of New York, after he and Thea are married. Thea, home from a visit to the doctor, exclaims her love ("When Did I Fall In Love"). At Dora and her husband Floyd's (who has retired from the police force) home, the corrupt backers of Jimmy Walker, Fiorello's competitor for mayor, meet. As one of the gang wants to have Fiorello killed at his public speech, Dora rushes to secretly warn Marie. However, Fiorello's campaign is in turmoil, with Ben being fired and his worry over Thea's deteriorating health. At LaGuardia's speech the gang's plan to kill him is foiled. But Thea dies, and Marie, Morris, and Neil have to tell Fiorello. The race for mayor is won by Jimmy Walker. Fiorello is inspired by tragedy to continue his campaign.