Dragonsheart — Jacqueline Farrell

When Isabella Wyndham-Brown returns to Edwardian England to celebrate reaching her twenty-first birthday, she is looking forward to becoming an adult away from the constraints of her well-meaning but interfering aunts and uncles. But events conspire against her: she learns that she cannot take control of her fortune until she is twenty-five and then finds disturbing evidence that her father had a mistress.

Nevertheless there are compensations, including meeting her handsome, but mysterious French cousin, Laurent, and being reunited with private detective Peter Bennett, who saved her life in Egypt. She is irresistibly drawn to both, but before she can get to know either, she discovers that her father may have found the family treasure, the long lost Dragonsheart diamond. And then her problems really begin...