Lost, baffled, and alone in Willesden's mean streets, Detective Constable Dangerous Davies is up against the cream of criminality. Newspaper theft (the work of organized crime?), household robbery (including cheese from the fridge), it's all grist to his mill. When Dangerous is beaten up, yet again, at a European Friendship dinner dance he reluctantly takes some sick leave.
Recuperating in Bournemouth he is approached by a member of the local Widows' Luncheon Club. She wants him to find out the truth about her husband's disappearance. Dangerous declines. It's against the rules. Back in Willesden a further beating helps change his mind.
So starts a double life of regular casework and moonlighting as Dangerous lurches into a mystery fit to confuse the great Holmes himself...