Dr Miles Bennell (Kevin McCarthy) recounts, in flashback, a fantastic tale about pod people replacing his patients and friends: "At first glance everything looked the same. But it wasn't. Something evil had taken possession of the town," he explains with some frazzle. Is it mass hysteria? Capgras syndrome? Or is there a more sinister explanation for the denizens of Santa Mira becoming blank and emotionless?

Don Seigel's superb 1956 version of Jack Finney's novel The Body Snatchers, doesn't have the militaristic dimension of Abel Ferrara's 1993 adaptation or that durable image of Donald Sutherland screaming in the 1978 version. But, steeped in post-war paranoia and such contemporaneous hot topics as psychiatry, it offers a snapshot of 1950s consciousness – a knot of influences that would feed into both the McCarthy trials and the golden age of science fiction.

The film still feels surprisingly modern. When people first complain that loved ones suddenly don’t feel like loved ones, Miles offers the kind of advice one still sees in government warnings: “You don’t have to be losing your mind to seek psychiatric help”.

The screenplay by Daniel Mainwaring is playful. "You're a forward wench", Miles tells Becky. Additional dialogue was reputedly supplied by Sam Peckinpah, who appears as a meter-reader. The film's producer Walter Wanger had just served a four-month sentence for shooting at his wife's lover (an incident that inspired Billy Wilder's The Apartment) and this helps explain the gloom that hangs over Invasion.

A happier ending, imposed by the studio, did little to lift the sombre mood. Thankfully, this is the shorter, spookier version. Neither age nor that awful Oliver Hirschbiegel remake shall weary Siegel's picture.