Who killed Marcus Steen, the theatrical tycoon with a fortune to leave to his young mistress Jacqui? And who killed Bill Sweet, the shady blackmailer with a supply of compromising photographs? Charles Paris, a middle-aged actor addicted to booze and women, decides to investigate by assuming a variety of roles, among them that of the mythical Detective Sergeant McWhirter. But, as Paris is about to discover only too painfully, impersonating a police officer is never a good idea.