After twenty years of devoted service to the police force, Irish police officer Peter Casey finds himself pensioned off and replaced by rookie Angus Ferguson, whom Casey considers a "contemptuous Scottishman". While delivering a complaint one night to the Casey apartment, Angus meets Casey's eldest daughter Maureen, who runs the motherless Casey household, and a mutual attraction arises between the young people. After retiring, Casey begins to get underfoot, and so Maureen and her sisters Patricia and Heloise encourage him to run for the post of alderman. Casey accepts the challenge, and with the help of his hooligan friend Gallagher, launches his campaign. Meanwhile, Maureen and Angus have been courting, and on the night that they are secretly married, Casey pleads with Maureen to never see the Scotsman again and tries to interest her in Michael Flaherty, a nice Irishman. When Casey's campaign runs short of funds, Heloise naïvely solicits a donation from her bookie friend, Joe Niklas. Upon learning the identity of his benefactor, Casey asks his constituency to elect his opponent, and his announcement sparks a barroom brawl in which Angus arrests him for disturbing the peace. After being pardoned by the judge, Casey chastises Maureen for her friendship with the Scotsman, and when Angus announces their marriage, the furious Casey orders the newlyweds to leave his house. Casey loses his daughter but wins the election as the voters, who admire his honesty, elect him alderman. On Christmas eve, he finally wins back Maureen when the familiy is reconciled at Maureen's bedside as she gives birth to twins.