Warning - Spoilers
Vera Hillyard killed her sister Eden in a fight over the child to whom both claimed to have given birth. Decades after Vera's execution, a writer approaches the women's niece for help in untangling the mystery. Vera's son Francis has disavowed his family, and their older half-sister and respective husbands were not present for most of the important events, so the only reliable witness is their niece Faith Severn. As a young teenager, Faith escaped the London Blitz by living with her aunts, an intruder in a suffocating mutual-admiration society. Brittle, housekeeper-extraordinaire Vera had devoted her life to her much-younger sister, shipping her son off to boarding school and living apart from her officer husband when Eden was orphaned at age 14. By 1939, Eden had grown into a beautiful and outwardly sweet young woman - the ideal of femininity according to her sister, and an ideal which Faith could never hope to achieve.
Eden joined the WRENs, leaving Vera (who was only in her late 30s) lonely and wishing for another child (the son she'd abandoned a decade earlier had become - or perhaps always was - a manipulator who found joy in psychologically torturing his mother), so no one was surprised when Vera announced her pregnancy. Jamie, however, was born 10 months after Vera's husband shipped out, thus casting doubt on his paternity. Three years later, Eden married a wealthy man and after an ectopic pregnancy left her infertile, she temporarily takes custody of Jamie from an ailing Vera.
This is where things get hazy. Faith, by this time, is a Cambridge student and receives much of her information second hand or in bits and pieces to be assembled later. Her narrative is full of "I heard" and "I think" but the gist of it is that Eden refused to return Jamie to Vera because she claimed to be his mother. More than 30 years later, Faith still doesn't know which woman was telling the truth. Was Jamie the result of an affair or of a rare (but not impossible) 45 week pregnancy? Or did Eden leave the WRENs more than a year before the war ended (Faith saw her aunt in mufti when Eden was allegedly still in the service) because she was pregnant, and then gave her son to Vera to raise? This time around, I thought Eden was Jamie's mother...until I didn't. And then I did.