Miss Maggie McCullen has been the keeper for the Port Carrick lighthouse for many years. She has never missed a night, keeping the big light going. And while the people in Port Carrick are grateful to her, they worry about her lonely life at the lighthouse. But they don't know that she has her cat, Sailor Boy, for company. Because Sailor Boy is no ordinary cat. He's a ghost cat. He can make himself visible or invisible, especially when visitors come to call and he wants to be mischievous. But when a fierce storm comes and Miss Maggie needs special assistance, Sailor Boy proves his worth.