Anni '70. Due ragazzi inglesi, il timido Enn e il più spigliato Vic, vanno ad una festa per conoscere delle ragazze. Qui però scoprono che le fanciulle in questione non sono altro che alieni provenienti da galassie lontane.

Margaret (Lena Headey) is a shy, pale, middle-class Englishwoman who is reluctantly engaged to her older, twittish neighbor Syl Monro (David Threlfall). Both bride- and groom-to-be still live with their mothers in the humdrum suburb of Croydon. However Margaret has been acting strangely ever since a vacation in Egypt, where she stayed with her mother's friend Marie-Claire (Catherine Schell). She secretly despises Syl, but does not resist when her mother Monica (Julie Walters), who has repressed the failure of her own matrimony, insists on marriage for the sake of social convention.