The Couple Next Door by Shari Lapena

Anne & Marco Conti are a happy couple. They have a new baby, Cora, and seem to be a very happy couple.
They are attending a dinner party next door, with Cynthia & Graham Stillwell. They don't have Cora with them, as Cynthia had insisted that it was "adults only". Unfortunately, Anne & Marco have left the baby alone in the house, as the babysitter had called and cancelled.
Anne & Marco are going over to the house every half hour to check on Cora. When Anne goes to check on the baby at 12:30 pm, the baby is not in her crib. The police are called and we are then taken through the next days on a roller coaster of guilt and backstabbing, etc.

This is a great thrill ride with all of the suspects involved in the kidnapping of Cora.
Very interesting, never boring, infinitely changing your feelings about every character in the novel.

http://www.sharilapena.com/