The four Gareth children, Alex, Penny, Robin and Naomi, have always led a very quiet life in London with their parents - until Dad suddenly gets ill abroad and Mum has to go out to look after him. They find themselves shipped off to stay with their Great Aunt Dymphna, who lives a wild life in an extraordinary half-ruin in Ireland.
Here, they are not only expected to look after themselves, but they also discover they have company - a mysterious boy who announces that he's on the run. The children hide him from pursuers - but who are they? And who is the boy? The children are determined to find out . . .