A suburban police station is understaffed due to a flu epidemic, and Sergeant Wilkins, under pressure to maintain staffing levels, is pleased to hear that three new recruits, straight from training school, are due shortly.
Before even arriving, the three policemen inadvertently assist some bank robbers into their getaway car, and are embarrassed when they learn the truth. The new constables are self-proclaimed intellectual and amateur psychologist PC Timothy Benson, former socially well-connected playboy and cad PC Tom Potter, and extremely superstitious PC Charles Constable. The arrival of WPC Gloria Passworthy, with whom Constable falls in love, and Special Constable Gorse completes the roster.
Out on the beat, the new constables try hard, but are less than successful. Benson nearly arrests a plainclothes detective, and Constable believes he has heard a murder being committed, but it turns out to be a radio play. Potter investigates a report of an intruder, but finds a young woman in the bath and engages in a civil conversation with her about her recently broken relationship. Gorse, tasked to patrol with a police dog, is unable to control it. They have better luck when a wages robbery takes place. Benson and Potter locate the getaway car, and all four engage in a confrontation with the thieves, arresting them and recovering the money.
Commended for his efficiency and excellent results, Inspector Mills is promoted to a training position and Wilkins is promoted to replace him. Charlie Constable gets his girl (with a little help from Sgt Moon) and stops being superstitious.