Eve Wingate (Valerie French) is holidaying in Cornwall and has just been for a swim when a strange figure appears and tells her he is taking her with him. Suddenly there is a flash of light and she is on a flying saucer with four other people, also spirited away from locations around Planet Earth, and they are all wondering where they are and what is happening. There are an American journalist, Jonathan Clark (Gene Barry), a German scientist (George Voskovec), a Russian soldier and a Chinese woman here, and they are not alone - that figure appears and announces himself only as "The Alien" (Arnold Moss). He has a mission for each of them...
Here's an example of Cold War paranoia from the fifties that provides a solution to all the world's problems that might not have gone down well with everyone. Based on the novel by John Mantley, and adapted by him as well, it's a variation on the then-recent The Day the Earth Stood Still in that the outer spaceman has an ultimatum for mankind that might well see the lot of us destroyed. The reason? These aliens have been forced to leave their home world and are looking for a new one, so Earth seems to be the best place, but they can't just barge in because of some kind of vague moral code.
What to do? I know, give Earth folks the power to annihilate themselves, which naturally will spare us any unpleasantness of blame for their foolish human ways. If this seems somewhat passive-aggressive on a huge scale, the nobody in the film seems to mind, and our five unlucky candidates for bringing this mass murder to the population are given a little round box each containing three capsules. When the candidate feels it is necessary to open the box, the lid will spring up and all they need to do is speak the longitude and latitude of the area they want to be destroyed, then every person in a three thousand mile radius is wiped out.
So of course, it's not the aliens bringing us to the brink, but silly old us. Who are they kidding? Is this supposed to be a metaphor for the powers that be creating nuclear weapons that can kill us all a few times over? The 27th Day doesn't seem quite so aware of such comparisons, and is more concerned with how to establish world peace which mostly seems to take the form of getting rid of those darned Communists. Not necessarily the ordinary folks in the Soviet Union or China or their satellite nations, but their leaders who have brought the Cold War upon us: the Russian and the Chinawoman aren't marked out as to blame for their authorities' behaviour.
The Americans don't seem to be repsonsible for the state of the world either, the notion that it takes two (or three?) to tango not being broached. On a more intimate level, after the five have been returned to terra firma, Eve tracks down Jonathan and they meet up in Los Angeles, only to become fugitives when the Alien broadcasts all over the world's television what is going on. Of course, they fall in love, but it's only Eve who has had the right idea: she throws the infernal box into the sea, never to be found. Although by the end of the 27th day, the time period that the aliens gave us to sort ourselves out, there is a happy ending, there's a certain tyranny of peace that sees the invaders, sorry, guests, get their way that comes across as unsettling; not quite as unsettling as killing all of us off, but that must have been in the back of the minds of those who had to live with them.