An American millionaire has just died. His sole legatee is a youthful indiscretion, a girl who is currently living in Italy. Two private eye detective agencies, in competition with each other, investigate. Combining business with pleasure, they search sunny Italy, but they only have one clue to find their heiress: she has three moles on the buttock. One of the private eyes falls in love with a gypsy who sings in nightclubs.
Tina, an old lady and detective stories buff, moves to town in the house of a god-daughter of hers whose husband is a private dick. She thinks she will be able to help him with his inquests. He does not agree with her and tries to discourage her by any possible means.
Three girls from Milan dreaming of a holiday in Rome arrive in the city by train and decide to pretend to be rich Danish girls to attract three nice guys... Three guys looking for easy-going girls offer them a guided tour through the most beautiful places of the city. The girls accept and make the guys spend a fortune, but one evening they get drunk and one of them incidentally reveals she's just from Milan. The guys get upset and set up a sort of revenge, but in the end they make it up.
When his girlfriend falls for a rich entrepreneur, an aspiring singer plots with the man's girlfriend so that they can get back their respective partners.
Sophia Loren plays a dual role, as both the sultry Queen of the Nile with a "man-a-night" appetite and a beautiful slave girl who takes her place and is wooed by a bodyguard who thinks she's the real monarch.