Some months later they realise that every woman of child-bearing age is pregnant with all indications that the pregnancies were caused by xenogenesis during the period of unconsciousness that has come to be referred to as the "Dayout".

When the 31 boys and 30 girls are born, they appear normal, except for their unusual golden eyes, light blonde hair and pale, silvery skin.

The Military Intelligence department learns that the same phenomenon has occurred in four other parts of the world, including an Inuit settlement in the Canadian Arctic, a small township in Australia's Northern Territory, a Mongolian village and the town of Gizhinsk in eastern Russia, north-east of Okhotsk.

The Russian town was recently "accidentally" destroyed by the Soviet government, using an atomic cannon from a range of 50–60 mi (80–97 km).

"[6] The writer Christina Hardyment, writing in The Times in 2008, commented that the book packed even more of a punch in an age of "genetic experimentation" than it had done in the 1950s.

[7] The dramatist Dan Rebellato, writing in The Guardian in 2010, called Wyndham probably the most successful British science fiction author since H. G. Wells and his books so familiar that people do not study them closely.

In Rebellato's view, The Midwich Cuckoos was, on rereading, "a searching novel of moral ambiguities where once I'd seen only an inventive but simple SF thriller", a book that questioned the assumptions of its narrator character.

It dealt, he argued, with the struggle between men and women at least as much as between people and aliens, touching on rape, abortion, childbirth and motherhood, with a subtext a great deal more subtle than the narrator's brusque story.

Rebellato observed, too, that Wyndham was writing in the 1950s under the Lord Chamberlain's censorship for obscenity, so his use of "misdirection, subtext, irony and ambiguity" were necessary to allow publication of his discussion of sexuality.

Christopher Wood was in the midst of writing a script for producer Lawrence P. Bachmann when the Writers Guild of America intervened.