"Fred and Nell's grandma is babysitting and the kids couldn't be happier. But hang on, there's something not quite right about her. In fact, she's acting very strangely indeed. And is that a spare eyeball? A tail? A striped tongue? That's NOT their grandma; it's an alien...RUUUUUUN! Find out how Fred and Nell overcome the invasion by grandmas from Mars (and get their own grandma back!)..."--Provided by publisher.