Bava, who'd once shot films for Roberto Rossellini and Raoul Walsh, used black and white for the last time on this project, and with its mastery of the noir vocabulary it helped establish the giallo.

The giallo gets its cinematic foundation in Mario Bava's wide-eyed "story of a vacation"

Plot and coherence aren't really so important as atmosphere and style and thrills, and these things [the film] possesses in abundance.

As expected, The Girl Who Knew Too Much has been infused with a compelling and thoroughly memorable sense of style that's ultimately revealed as the one bright spot within a film that's otherwise fairly interminable.