On the day of the 'Royal Wedding' in July 1981 at a house party on the banks of the Thames, a little girl wanders off on her own. Her doll is found floating in the river, but of the girl herself there is no sign. Twenty years on and Antonia Darcy, divorcee and assistant librarian at the Military and Naval Club, still puzzles over the disappearance of Sonya Dufrette. Ably assisted by her new admirer, Major Payne, Antonia embarks on solving the mystery of the girl's disappearance.