The village of Larking is one of those quiet small towns where everyone fancies they know everything about everyone else, especially quiet-living widows like Grace Jenkins, bringing up one daughter, now away at university. It's so small that Harry Ford the postman does his round on a bicycle - and he's grateful for it when he finds Mrs. Jenkins dead in the road not far from home, clearly a victim of a hit-and-run driver the previous night. But the formalities of a road traffic accident require a formal identification and an autopsy, so Henrietta is recalled from school to identify Grace Jenkins.
Then Dr. Dabbe delivers his report, and the case goes to Sloan of the CID rather than Harpe of Traffic Division - because Grace Jenkins was run over twice, once each way, and it looks like murder by motorcar. But the most troublesome fact has no immediate bearing on the death, and goes to show that even in a village, some secrets can be kept: Dr. Dabbe's expert opinion is that not only did the deceased never give birth to any child, but she's not likely ever to have been married, either.
So Henrietta isn't Henrietta Jenkins - but who is she? Somebody has been very thorough in covering his or her tracks; the Jenkins cottage was broken into, and Henrietta's birth certificate is missing. Where do you begin when a very discreet woman covered up all traces of her own identity and that of the child she raised almost from birth? Worse, Grace brought Henrietta to Larking in the middle of WWII - not the best time to try to find records for.
Very good character development - Henrietta has lost the only mother she ever knew, not once but twice, and has to question everything Grace ever told her, and it hits about as hard as you'd expect. There's comic relief, too, when Sloan and Crosby begin tracing people Grace Jenkins mentioned having worked for once, and they find out a lot about her sense of humor. The murder is a fair puzzle, with all the clues artfully concealed in plain sight, if you're paying attention.