"The Couple Next Door" is a psychological thriller novel by Shari Lapena. The story revolves around a young couple, Anne and Marco Conti, who leave their baby at home while attending a dinner party next door. When they return, they discover their baby has been kidnapped, leading to a frantic search and unraveling secrets. As the investigation unfolds, the couple faces scrutiny from the police and their neighbors. The narrative explores themes of trust, betrayal, and the complexities of relationships, ultimately revealing the dark truths hidden behind seemingly perfect lives.