A very straight forward mystery. As one reviewer said its not six bodies piled up with crucifixions and mutilation. Just one missing baby and a murdered nanny.
Methodically told, we have a young rather strange parents - a father who seems disassociated from his baby son, and a mother who is passionately fond of her baby but who seems to be under orders to keep him in charge of his nanny. A secretary who seems to run the show and various side characters particularly since the young husband is a leading businessman as well. Wife is a former showgirl but she does not seem to have many friends or colleagues either.
We have a police officer who just starts work and this is her first case. It is also something that she can emotionally relate to - she gave up a baby at birth and gets more and more emotionally involved in the case as time goes by. She feels personally invested in the case and that she has to solve it, not just solve it but return baby Charlie back to his mother and father safely.
There is no inkling at all who is the actual culprit - that is the part that was good. You only get an idea almost at the end where Kate's (our detective) own past helps her to pinpoint who the actual kidnapper and murderer are.