The Mennyms are faced with a crisis when plans to build a motorway straight through their home are announced. They've successfully survived living on Brocklehurst Road for forty years, carefully keeping the secret of their rag doll identity under wraps. But news of the motorway forces them to confront a cruel ultimatum: they can be destroyed with the house, or they can move out into the countryside. Either way the consequences will be devastating. As they try to adjust to new and frightening circumstances, they worry — will they be able to keep their secret from the outside world?