Betty, the pretty daughter of Jonathan Brownlee, a retired capitalist, is impulsive and mischievous, delighting in pranks that keep her father and the servants of the household in perpetual apprehension. Brownlee's stock phrase is "Betty Be Good," constant, though rather futile, appeal on his part to the high-spirited girl, who tells her friends she is weary of being lectured on her tomboy achievements. Peter Madison, mayor of the city, is at enmity with Millionaire Brownlee over political matters. He has a son, Jimmy Madison, who is masquerading as a uniformed policeman in order to detect grafters on the force. Brownlee secures what he believes to be evidence of political crookedness on the part of the mayor. The documents are lost when Betty, in one of her escapades, drives off with the car in which her father has left them. Jimmy arrests Betty for stealing the car and papers, being unaware of her identity.