One night, young astronomy enthusiast David McLean (Jimmy Hunt) sees a spaceship crash into a nearby sandpit.
His father (Leif Erickson) goes to investigate, but comes back changed. Where once he was cheerful and affectionate, he’s now sullen, harsh and snarlingly rude.
Others fall into the sandpit and begin acting the same way: cold, ill-tempered and conspiratorial.
David deduces that aliens are taking over the bodies of humans, but he’ll soon discover there have been far more of these terrible thefts than he could have imagined.
The young boy finds some serious help in Dr Pat Blake (Helena Carter) and her fiancé, brilliant astronomer Dr Stuart Kelston (Arthur Franz).
Soon they meet the aliens – green creatures with insect-like eyes – and their leader, a large, silent head encased in a glass globe with ceaselessly shifting eyes and tentacles.
Ultimately, the military arrives and saves the day.
Several well-known actors appear in very small (uncredited) cameos, including; Todd Karns, Lock Martin, Milburn Stone, Barbara Billingsley, Robert Shayne and Douglas Kennedy.
Dr Pat Blake
Dr Stuart Kelston/Narrator
Mr George MacLean
Mrs Mary MacLean
William Cameron Menzies