Little Face by Sophie Hannah

Alice Fancourt is a new mom. She leaves her daughter alone with her husband, David, for the first time and when she returns home is stunned to discover that their baby has been switched with another. David doesn't agree. Is Alice suffering from a severe case of postpartum depression or lack of sleep? Or is something more sinister going on? Alice and David live with David's mother, Vivienne, who can be extremely controlling. Also, David's first wife, Laura, was murdered outside the family home, the Elms. The police don't really believe that a crime has been committed. Alice does have detective Simon Waterhouse on her side, but is his interest in Alice only job-related? Then, a week later, Alice and the baby go missing. Little Face is like Philippa Gregory's The Little House, a memorable psychological novel from ten years ago.