The big old house at Number 5 Brocklehurst Grove looks like any other. Yet inside, nothing is as it seems. A family of children, parents, and grandparents, are living happily in a home filled with love and magic. It's a house no one from the "real world" has entered in forty years...or else someone would have discovered an astonishing secret! But now the Mennyms wonderful and very different world is about to be turned upside-down...and it could mean the end of them all.