The fake private detective Mike Spillone is hired by two old ladies to find out if Brigitte, the wife of their nephew Otello Bellomo, has a lover. Brigitte is a physician but the two aunts are unaware of the fact. While investigating, Mike and his assistant Johnny discover Brigitte with a prospective patient, the marquis De Vitti who was shot by the husband of the woman he tried to seduce. Afterwards Spillone finds her with her husband who he believes to be her lover.
| Actor | Role |
|---|---|
 TotòMichele Spillone detto Mike | Michele Spillone detto Mike |
 Vittorio De SicaMarchese Vittorio De Vittti | Marchese Vittorio De Vittti |
 Abbe LaneDottoressa Brigitte Baker | Dottoressa Brigitte Baker |
 Titina De FilippoMadre del marchese De Vitti | Madre del marchese De Vitti |
 Germán CobosAvvocato Otello Bellomo | Avvocato Otello Bellomo |
 Agostino SalviettiGennaro | Gennaro |
 Rafael BardemProfessor Elia Vagoni | Professor Elia Vagoni |
| FFranco CoopIl maître della 'Conchiglia' | Il maître della 'Conchiglia' |
 Fulvia FrancoCaterina | Caterina |
 Dante MaggioCameriere | Cameriere |
 Pierre MondyRomeo | Romeo |
 Luigi PaveseCapo dell'agenzia investigativa | Capo dell'agenzia investigativa |
| AAmelia PerrellaIda | Ida |
| BBenedetta Rutiliinfermiera | infermiera |
 Tecla ScaranoZia Ada Barbalunga | Zia Ada Barbalunga |
 Teddy RenoSelf | Self |
 Darry CowlEgisto | Egisto |
 Arturo BragagliaIl signore al comizio (uncredited) | Il signore al comizio (uncredited) |