When Della Thomson arrives to stay with twelve-year old Fran on the island of Broray for a week , Fran is full of hope and expectation. But Della is a surly and unsociable girl from Glasgow, dressed from head to foot in intimidating black. She hardly touches her food and seems to sneer at everything and everyone, and family life seems to disgust her. What's more, she's a thief! Fran thinks things couldn't get any worse - until she discovers the graffiti - the letter D in royal blue spraypaint - all over the island. Who else could it be? Then one day, Fran and Della take a walk together, and with Del's encouragement, end up on Devil's Leap - a notoriously dangerous mountain- and Del falls and hurts her ankle. The girls are in grave danger and it's time for Della to get real. And finally open up to Fran . . .