With The Girl Who Knew Too Much, director Mario Bava planted the seed that would evolve into the sub-genre known as the giallo. In fairness, it doesn't much resemble the films that would typify this genre in the 70's. Bava's next film Blood and Black Lace would truly be the definitive template film that would inform the giallo. But there is no doubting that some of the recurring motives and ideas of this most Italian film genre began here.

As the title suggests, The Girl Who Knew Too Much is indebted to Alfred Hitchcock more than anything else. The idea of an innocent thrust into the middle of a deadly situation is one Hitchcock used many times. While the romantic sub-plot and moments of light comedy also recall his work. These latter two elements are mainly what mark out TGWKTM as a cross-over film, as they are certainly not features of giallo cinema as it would develop. But the light, comic approach is one of the things that make this one of the most playful and upbeat films that Mario Bava ever made. Unlike his three other gialli, this film actually has sympathetic characters. While it doesn't have the melodramatic tendencies that those ensemble movies had either. The approach is much more restrained, with a fairly simple amateur sleuth narrative being the framework. Completely different too is the black and white aesthetic. Bava is of course rightfully famous for his masterful use of colour but in this film he shows that his use of light and contrast is just as impressive. This is a very handsome looking movie. Letícia Román adds to this aesthetic too of course, seeing as she is a very beautiful woman. Visually, this is a terrific film. Story-wise, it's certainly less interesting. The fairly mechanical plot is sufficient enough in taking us from A to B but it isn't particularly memorable. But it does introduce some of the motives that would go on to form an important part of giallo cinema such as the convoluted mystery, the bizarre reasoning for murder and the importance of optical subjectivity as well as the focus on style over substance.

The Girl Who Knew Too Much is a film that should be seen by fans of Mario Bava as well as dedicated students of all things giallo. It's a film that is as breezy and light as the genre ever got. It's a lovely and beautiful looking flick from a master film-maker.