Based on Frank Crisp’s novel The Night Callers, Night Caller From Outer Space follows Scientist Jack Costain (John Saxon) who investigates a meteorite in the British countryside, discovering that it is an alien device from Ganymede, a moon of Jupiter. They capture a tall alien and take it to their lab, but it escapes.

Shortly thereafter, teenage girls begin to go missing after answering an advertisement in ‘Bikini Girl’ magazine. It turns out the alien wants to use women from Earth for breeding purposes!