The Spider's Web

When a teenage boy dies in a tragic joy-riding accident, his parents are not only distraught, but convinced that their well-behaved son would never behave like this. They approach Dr Sam Ryan and ask her to do a second post-mortem on the body. Sam is reluctant to go behind the back of her colleague, but something in the boy's file makes her go ahead - and what she finds is strong evidence that he had been strangled before being put in the car...
But none of the police officers involved in the investigation are convinced by her findings, and it is up to Sam to make her own, surreptitious enquiries.