Ruth, Naomi, Rachel and Phoebe Conroy love reading and having fun more than anything else. So the sisters are horrified when they learn that their parents are sending them away to Cumbria for the summer, to stay with their fearsome grandmother: Big Grandma. Big Grandma is strict, makes them do chores and doesn't let them have any fun – but worst of all, she refuses to let the girls read any books. Determined to enjoy their summer, the sisters decide they aren't going to put up with their grandmother's tough regime, and in doing so they somehow manage to cause inordinate amounts of chaos . . .
But as the girls search for alternatives to Big Grandma's way of life they slowly start to understand its appeal, just as she starts to understand them. Are the two generations more alike than they think?