Claudia Milmont has lived most of her joyless life with her grandparents, though her mother enjoys the fringes of society in London. When Claudia's Aunt Sophie dies, a whole new world opens up for her. Cantankerous Sophie has instructed that her diamonds be buried with her - and Claudia is determined to help her cousin retrieve them. But the charming Sir Hillary Thoreau, a nonesuch, is co-executor of Sophie's will and he's keeping a sharp eye out for any mischief - and for Claudia, too, it would seem.