The Mennyms are a suburban family, living what seems to be an ordinary life, which in reality has at its core a devastating secret to be kept at all costs from the outside world. They have successfully survived in Brocklehurst Grove for forty years - but then they find out about the motorway that has been planned to go straight through their house.
The Mennyms have two options: they can be destroyed with the house, or they can move out into the country and try to carry on. But far away from the safety and familiarity of Brocklehurst Grove, anyone might discover the secret of their very existence.