I've read all the previous nine books in the series, and this one is the most disappointing.
The plot is full of holes and incomprehensible coincidences.
First of all the coincidences: it turns out that Diane was raped by her foster brother in a random assault with several other men. She was not targeted by her foster brother, he just happened to be one of the assailants. This is quite amazing as it occurred in Birmingham, a major city. Second coincidence, her biological father, who she had not seen since she was a small child, just by chance was also at the scene of the assault. If this happened in a village with a population of ten people, I could perhaps believe it, but not in a city of millions.
The storyline with regards to Ben, is no better. Despite no obvious evidence, Ben is convinced that the family of a drowned girl are involved in her death. By some amazing sixth sense he is able to locate the body of a baby, which he instantly knows must be the child of the estranged daughter of the family. He then discovers that her father was the father of the dead baby. This leads him to conclude that her brother must have drowned his younger sister, because he was traumatized by knowing of the incest committed by his father. Obvious really.