Walking through a London park one afternoon, wealthy, jaded fashion photographer Thomas (Hemmings) snaps some photos of a couple embracing in the distance. Noticing the intrusion, Jane (Redgrave) – one of the subjects – chases after him, demanding the negatives. So Thomas slyly hands over an empty roll. Later, after developing the film, he discovers he may have unwittingly photographed a murder in progress.

Antonioni's existential mystery scandalized some in the 1960s with its cool, casually erotic atmosphere of sex and drugs, but still made a sizeable dent at the box office. In addition to the film's central puzzle – was there a homicide or not? – Hemmings himself is a kind of cipher, playing a detached, unsmiling artist bored with his decadent life. With its mod flavorings and occasional surrealist touches – like a pantomime tennis game – "Blow-Up" is an intriguing, unconventional thriller that makes you question the nature of reality and illusion.