Over Invernesshire in Scotland there have been reports of a bright meteor crashing in the remote countryside. At a local inn, barmaid Doris (Adrienne Corri) listens to the radio and an interview with a professor about the phenomenon. That professor (Joseph Tomelty) is currently lost in the vicinity, accompanied by reporter Michael Carter (Hugh McDermott), as they try to track down the site of the meteor landing. Also in the area is Doris's old boyfriend Albert (Peter Reynolds), who is on the run from the police having escaped from prison on a murder charge. He shows up at the inn and poses as a hiker who has lost his wallet and the owners, Mr and Mrs Jamieson (John Laurie and Sophie Stewart) agree to let him stay. But as the professor and Carter arrive too, there's an uninvited guest on the way - from outer space...
Written by John C. Mather and James Eastwood, Devil Girl from Mars has the look of a filmed radio play from the start, with its collection of characters each bearing their own little drama to act out before the greater drama of a psychopathic space girl to contend with. Obviously an attempt to match the American science fiction efforts of the time, the story plonks an intergalactic enemy down in one of the quietest areas of Scotland in a reversal of the "Earth astronauts discovering a race of women on another planet who are lacking male company" plotline: see Queen of Outer Space and Cat-Women of the Moon as evidence. Here the alien woman is looking to conquer the world and take back a bunch of lads, willing or not, to sustain the Martian bloodlines as the Martian men aren't up to the job any more.
There was a war between the sexes on Mars, you see, and the ladies emerged triumphant, with their superior technology. Despite this, they don't seem to have invented a space ship that runs quietly, judging by the tremendous din the Devil Girl makes in hers. The villainess (played by Patricia Laffan) dresses casually in a PVC miniskirt, helmet and cape, and can barely conceal her contempt for us Earthlings. She has landed in Scotland by mistake, because she meant to go to London but part of her flying saucer broke off, necessitating repairs - in four short hours she'll be off again and world domination will be in her grasp. Can the folks at the inn do anything to stop her in her tracks?
It doesn't look likely as Nyah (that's her name, pronounced "Nye-ah", not as in the playground taunt "nyah-nyah n-nyah nyah") erects an invisible wall around the inn and shows off her cumbersome giant robot, Chani, who blows up a tree and an abandoned truck to demonstrate his awesome power. You would have thought that the lonely blokes of Earth who would jump at the chance of securing a Martian girlfriend would be the most likely candidates to go, but Nyah isn't picking up just anybody, oh no, as witnessed by her zapping an inferior specimen (i.e. a bit part actor with no lines) who crosses her path. Funnily enough, none of the characters like Nyah's offer, and the promise of sex with no obligations doesn't appeal to the menfolk, indeed the subject never comes up.
Although the stunning event of an invasion from Mars surprises the characters, they are very easily distracted by their own personal problems. Carter recognises Albert and he has to hide in the attic (and a later encounter with Nyah leaves him mouthing Martian propaganda), as Doris frets over him, and Carter strikes up an extremely fast moving romance with an English model (Hazel Court) which Nyah threatens to break up. Mr Jamieson just wants a drink. The film adopts a pattern of heated conversations at the inn followed by trips outside to see the flying saucer, meaning a light monotony settles in early on. The professor wants to learn more about Nyah's scientific achievements and offers to be her guide if she spares everyone's lives, but she's not so sure. Who will she take? You'll have to watch and see, if you get that far; Devil Girl from Mars is just too polite to build up any excitement, and even if it does have a memorable villain it seems too reticent to do much with her. Music by Edwin T. Astley.