One morning, the English village of Midwich is suddenly cut off from the rest of the country by an inexplicable phenomenon which causes every human and animal within a circular perimeter to fall asleep. Gordon Zellaby, a middle-aged scientist with a much younger wife, Anthea, is struck down as he is on the telephone with his brother-in-law, Major Alan Bernard. The soldier alerts the authorities, who investigate - a policeman cycles over the perimeter and falls off his bike, a low-flying plane crashes when the pilot succumbs. After an hour or so, Midwich wakes up again as inexplicably as it fell asleep and an inconclusive investigation notes that some unknown signal seems to have been responsible.
In the ensuing weeks, it turns out that every woman of child-bearing age (including Anthea) is pregnant. The villagers react in different ways to the news, but Gordon and the local GP, Dr Willers, are first to realise that the unnatural impregnations are connected with the blackout. Twelve children are born on the same night, and grow rapidly - all have blonde hair, 'strange' eyes and unusual mental powers. When Anthea gives her son David milk that is slightly too warm, the baby telepathically forces her to punish herself by sticking her hand into boiling water. Gordon, fascinated and disturbed by the children, discovers they have a group mind, that anything one of them learns is know to all the others.
Four years later, the children are the size of human ten-year-olds and have demonstrated their powers by harming normal children or adults who threaten them. They opt to live together and adopt Gordon as their teacher. Other groups of alien children have been born around the world, but only in Midwich and Russia have they survived. Alan worries that the children are evil and inimcal to humanity, arguing for their termination, but Gordon hopes that they can be reached intellectually and benefit the planet. The adults of Midwich become more resentful of the children: when a careless driver who nearly runs one over is telepathically forced to crash into a wall, his brother stalks them with a shotgun and is driven to blow off his head.
News comes in that the children in the Soviet Union have been vaporised by an atomic missile that has also destroyed the whole community where they lived. A Midwich mob marches on the children, but are turned against each other and Alan is pushed into a complete nervous collapse by a telepathic attack. David, speaker for the group mind, tells Gordon that the children will soon be able to form new colonies and spread over the world. Now convinced that the children must be destroyed, Gordon carries a bomb into the classroom, projecting a mental picture of a brick wall to prevent them realising the danger. The children assault him telepathically, crumbling the wall, but the bomb goes off. Gordon has sacrificed himself to kill the children.
