Engineer Quiller is the inventor of bullet proof glass that puts jewel thieves out of work and threatens to ruin an insurance company because jewellers no longer bother to get insured. This made Quiller a rich industrialist. Since he is played by Adriano Celentano, we are also treated to the usual self-mocking pseudo-machismo. However, Quiller's private life is in a shambles.
Tilli, played by Eleonora Giorgi, is a talented pickpocket and part of a lower class family of specialized criminal professionals. There seems to be nothing much wrong with her private life, other than too much routine and the occasional (routine) trouble with the police. She has a giving personality and dreams of a life on the side of someone like gentleman thief Arsène Lupin -- a literary figure who could be seen in the popular French television series
Arsène Lupin (1971) around that time.
Based on this constellation, the plot of a romantic crime comedy almost writes itself. The plot is in fact as good as the constellation promises, and the execution is great as well. It is certainly not subdued, but in retrospect it somehow feels that way. Maybe this is because you would expect this kind of comedy to go over the top all the time, which it doesn't. There is comical exaggeration, but not to the degree I would have thought, and the physical humor never turns into the slapstick type. This is why I am calling the film very nice rather than, for example, hilarious. This might actually be a general feature of Italian comedies from that time.
In places I was reminded of the Olsen Gang, which I think also owed its inspiration to Arsène Lupin. But where that Danish series transferred the basic idea into the petit-bourgeois milieu, this film lives from the tension brought by a twisted Cinderella plot.
Overall, this is a unique little gem that is well worth watching, and then perhaps re-watching after a while.