A gang of crooks slinks into a London house. When PC Spiffkins investigates, he is coshed and dragged inside, his whistle falling to the pavement.

A girl and her friend bid each other goodnight after leaving a cinema showing Ivor Novello in The Constant Nymph. The girl sees the policeman's whistle on the pavement and blows it. Pandemonium breaks out and soon the whole police force is closing in on her.

The terrified girl tries to dispose of the whistle, but it is found, entry is forced into the house and she becomes caught up in a gunfight between police and crooks. She manages to get hold of a gun and, although nearly rendered unconscious by the fall of a bust, she manages to hold up a considerable number of the gang. As the police arrest them, she takes the opportunity to race home and take refuge in her bed.

The following morning she is roused by her landlady, as a police car is waiting for her. She is whisked off to the station to receive the congratulations of the whole force and the thanks of the injured Spiffkins. As a reward she is given an umbrella from the Lost Property Office.

She takes this to a pawnbroker and when a small boy in the shop starts to blow a whistle she beats a hasty retreat and races away for dear life.