Murder is Easy by Agatha Christie

Luke Fitzwilliam, a retired policeman, meets a woman on a train who claims a serial killer is targeting people in her village. When she is later killed in a hit-and-run, Luke investigates the village under a false identity. As he digs deeper, he finds a chilling pattern and a community full of secrets. The story builds steadily toward a shocking conclusion that challenges his instincts. It’s a tense standalone mystery where murder hides behind a peaceful facade.