Quattro mosche di velluto grigio brings to an end both Dario Argento’s initial, frenetic two years of directing (three films in two years) and his ‘zoo- symbolic’ trilogy: so we can say the first period of his cinema comes to a close as well […]. The setting moves between Milan and Turin, in an evocative urban symbiosis photographed in a cool and polished style by Franco Di Giacomo. Ennio Morricone completed the last of his three initial scores for Argento (the two would meet a quarter of a century later for La sindrome di Stendhal), the most ‘pop’ and least experimental. The screenplay was written by Argento’s friend and disciple Luigi Cozzi, later a director himself and a fine critic of the master’s oeuvre, together with the director and Mario Foglietti. […] Argento’s third film is yet another reflection on perspective: not the last, perhaps not even the most linguistically decisive, but certainly the one in which the interaction with the writer’s other obsessions (madness, staging, dreams, masks) is accomplished and, finally, ‘dismissed’. Massacres and lies, tension and deception, childhood trauma and revenge served cold are mixed – here as never before or again in Argento’s films – with the mechanisms of comedy. In this context, Argento adds repeatedly misleading elements, reminding us – along with Hitchcock and Fritz Lang – that, if ‘hangmen also die’, the flashbacks lie too. Or flashforwards.

Roberto Pugliese in Argento vivo. Il cinema di Dario Argento tra genere e autorialità, curated by Vito Zagarrio, Marsilio, Venice 2008

I wanted to tell the story of a couple, a husband and wife who live under the same roof but who know nothing about each other, and could have unmentionable, dreadful secrets. […] In this film, I pushed everything I had learned up to that point; I tried to get the most out of it by using the most unusual equipment. For the final sequence, I used the Pentazet, a camera that belonged to the University of Leipzig, which used it to study the smelting of metals; the only one in the world to achieve a shooting speed of 18,000 and – in theory – 30,000 frames per second. We managed to get to 12,000 frames using a special process. The end result is a beautiful, very smooth, slow-motion sequence.

Dario Argento, Intervista a Dario Argento. L’occhio che uccide, curated by Fabio Maiello, Edizioni Scientifiche Italiane, Naples 1996