Paul and Rosa were not looking forward to their holiday on a lonely farm by the sea without their parents - though there was that old stone fort to explore. But when they follow the enormous ginger cat up the steep steps to Ballig Fort, neither of them is prepared for the exciting secret world they uncover. Before long, the children are involved in a battle to save and care for a whole zoo of wild creatures, including sea-birds damaged by oil, a jackdaw called Bertie and a friendly black labrador!